Absence of glucocorticoids augments stress-induced Mkp1 mRNA expression within the hypothalamic–pituitary–adrenal axis

in Journal of Endocrinology

Stress-induced activation of hypothalamic paraventricular nucleus (PVN) corticotropin-releasing hormone (CRH) neurons trigger CRH release and synthesis. Recent findings have suggested that this process depends on the intracellular activation (phosphorylation) of ERK1/2 within CRH neurons. We have recently shown that the presence of glucocorticoids constrains stress-stimulated phosphorylation of PVN ERK1/2. In some peripheral cell types, dephosphorylation of ERK has been shown to be promoted by direct glucocorticoid upregulation of the MAP kinase phosphatase 1 (Mkp1) gene. In this study, we tested the hypothesis that glucocorticoids regulate Mkp1 mRNA expression in the neural forebrain (medial prefrontal cortex, mPFC, and PVN) and endocrine tissue (anterior pituitary) by subjecting young adult male Sprague–Dawley rats to various glucocorticoid manipulations with or without acute psychological stress (restraint). Restraint led to a rapid increase in Mkp1 mRNA within the mPFC, PVN, and anterior pituitary, and this increase did not require glucocorticoid activity. In contrast to glucocorticoid upregulation of Mkp1 gene expression in the peripheral tissues, we found that the absence of glucocorticoids (as a result of adrenalectomy) augmented basal mPFC and stress-induced PVN and anterior pituitary Mkp1 gene expression. Taken together, this study indicates that the presence of glucocorticoids may constrain Mkp1 gene expression in the neural forebrain and endocrine tissues. This possible constraint may be an indirect consequence of the inhibitory influence of glucocorticoids on stress-induced activation of ERK1/2, a known upstream positive regulator of Mkp1 gene transcription.

Abstract

Stress-induced activation of hypothalamic paraventricular nucleus (PVN) corticotropin-releasing hormone (CRH) neurons trigger CRH release and synthesis. Recent findings have suggested that this process depends on the intracellular activation (phosphorylation) of ERK1/2 within CRH neurons. We have recently shown that the presence of glucocorticoids constrains stress-stimulated phosphorylation of PVN ERK1/2. In some peripheral cell types, dephosphorylation of ERK has been shown to be promoted by direct glucocorticoid upregulation of the MAP kinase phosphatase 1 (Mkp1) gene. In this study, we tested the hypothesis that glucocorticoids regulate Mkp1 mRNA expression in the neural forebrain (medial prefrontal cortex, mPFC, and PVN) and endocrine tissue (anterior pituitary) by subjecting young adult male Sprague–Dawley rats to various glucocorticoid manipulations with or without acute psychological stress (restraint). Restraint led to a rapid increase in Mkp1 mRNA within the mPFC, PVN, and anterior pituitary, and this increase did not require glucocorticoid activity. In contrast to glucocorticoid upregulation of Mkp1 gene expression in the peripheral tissues, we found that the absence of glucocorticoids (as a result of adrenalectomy) augmented basal mPFC and stress-induced PVN and anterior pituitary Mkp1 gene expression. Taken together, this study indicates that the presence of glucocorticoids may constrain Mkp1 gene expression in the neural forebrain and endocrine tissues. This possible constraint may be an indirect consequence of the inhibitory influence of glucocorticoids on stress-induced activation of ERK1/2, a known upstream positive regulator of Mkp1 gene transcription.

Introduction

Corticotropin-releasing hormone (CRH) neurons of the hypothalamic–pituitary–adrenal (HPA) axis integrate stress-dependent changes in neural input and direct negative feedback effects of glucocorticoids (Dallman et al. 1987, Sawchenko et al. 1996, Bali et al. 2008). Excitation of CRH neurons is often coupled to not only CRH neurohormone secretion but also altered gene expression and neurohormone synthesis (Kovács & Sawchenko 1996, Watts 2005, Pace et al. 2009). Recent evidence indicates that a molecular element of this coupling process within CRH neurons is phosphorylation/activation of ERK1/2 (Khan & Watts 2004, Khan et al. 2007, 2011). ERK1/2 are members of the MAP-kinase family. MAP-kinases are essential intracellular signaling proteins for virtually all cell types, including neurons and endocrine cells (Grewal et al. 1999). We recently have reported that acute exposure to psychological stress (restraint) increased the activated (phosphorylated) form of ERK1/2 in the hypothalamic CRH neurons, and this ERK1/2 activation was constrained by the tonic activity of glucocorticoid (Osterlund et al. 2011).

The active phosphorylation state of ERK1/2 is regulated by both the kinase MEK and by phosphatases, including MAP kinase phosphatase 1 (MKP1, also known as DUSP1) (Keyse 2000, Patterson et al. 2009). MKP1 is a dual specificity phosphatase that inactivates MAP-kinases by dephosphorylating tyrosine and threonine residues essential for catalytic activity (Camps et al. 2000, Theodosiou & Ashworth 2002). A key feature of MKP1 is that its encoding gene (Mkp1) is rapidly induced in a wide range of cell types by a large number of excitatory stimuli (Sun et al. 1993, Caunt & Keyse 2013). Interestingly, in vitro studies found that glucocorticoids increase Mkp1 mRNA levels in a variety of peripheral cell types and cell lines (Clark 2003, Clark et al. 2008). Glucocorticoid treatment in mice has also been shown to rapidly increase Mkp1 mRNA in the lung, spleen, and liver (Wang et al. 2008, Vandevyver et al. 2012). In vitro studies have also shown that glucocorticoid suppression of some MAP-kinase-dependent cellular processes depends on glucocorticoid-mediated upregulation of Mkp1 gene expression (Kassel et al. 2001, Issa et al. 2007, Zhou et al. 2007, Komatsu et al. 2008, Nicoletti-Carvalho et al. 2010, Burke et al. 2012).

Glucocorticoids provide a protein-synthesis-dependent negative feedback inhibition of the HPA axis that is evident within 1–3 h after glucocorticoid treatment (Dallman et al. 1987, Shipston 1995, Osterlund & Spencer 2011). This short-term glucocorticoid negative feedback action is probably due to rapid glucocorticoid rapid induction of one or more genes that encode proteins important for the coupling of cellular excitation with (neuro)hormone secretion (Shipston 1995, Osterlund & Spencer 2011). We considered the possibility that glucocorticoid suppression of stress-induced ERK1/2 activation in hypothalamic paraventricular nucleus (PVN) CRH neurons depends, at least in part, on rapid glucocorticoid upregulation of Mkp1 gene expression. To determine whether induction of the Mkp1 gene could be a mechanism for short-term glucocorticoid regulation of the HPA axis, we examined Mkp1 mRNA levels (in situ hybridization) in the hypothalamic PVN, medial prefrontal cortex (mPFC), and anterior pituitary of male rats subjected to acute stress and corticosterone (CORT) manipulations. The PVN contains the HPA axis-related CRH neuron cell bodies. For comparison purposes, we also examined Mkp1 mRNA levels in another brain region important for the modulation of HPA axis activity, the mPFC (Radley et al. 2006, Weinberg et al. 2010), as well as in an additional anatomical element of the HPA axis, the anterior pituitary. For these studies, we challenged rats with the acute stressor restraint, which is considered a moderate-intensity psychological stressor (Herman & Cullinan 1997, Dayas et al. 2001, Pace et al. 2005). We manipulated CORT levels by either removing endogenous CORT (adrenalectomy) or by treating rats with an acute injection of CORT. Although to date there has been very limited study of Mkp1 gene expression in mammalian brain, there is evidence for it being regulated in an activity-dependent manner, contributing to neuronal axonal plasticity, and being associated with major depressive disorder (Sgambato et al. 1998, Kodama et al. 2005, Doi et al. 2007, Jeanneteau et al. 2012).

Materials and methods

Animals

Young adult male Sprague–Dawley rats (Harlan Laboratories, Indianapolis, IA, USA) weighed between 280 and 305 g at time of experimentation were housed two per-cage. The colony room lights were maintained on a 12 h light:12 h darkness cycle and rats were given rat chow (Purina Rat Chow, Ralston Purina, St Louis, MO, USA) and tap water and allowed to feed and drink ad libitum. Rats were given at least a 2-week acclimation period to the colony room before initiation of experimental procedures. All experiments were performed during the first half of the rats' inactive period, when basal CORT secretion is at its circadian trough. Handling and testing of all rats were approved by the University of Colorado Institutional Animal Care and Use Committee.

Surgery

Rats were adrenalectomized bilaterally (ADX) or were sham-ADX under halothane anesthesia. Adrenal glands were excised and removed through bilateral incisions that were made through the dorsal-lateral skin and peritoneal wall in close proximity to each kidney. Sham-ADX rats experienced the same surgical procedure as ADX rats, except that adrenal glands were left in place after their localization. All ADX and sham-ADX rats were given 4 days to recover from surgery before the experimental test day. ADX rats were given 0.9% saline drinking water and allowed to drink ad libitum.

Restraint stress

Acute stress challenge consisted of placing rats in clear plexiglass tubes (23.5 cm in length and 7 cm in diameter; with multiple air holes). The size of the tube restricted lateral, forward, and backward movement but did not interfere with breathing. Restraint is widely accepted as a psychological stressor within the stress neurobiology field, which has not only a conceptual basis, but is also supported by a study on neurocircuit activity (Dayas et al. 2001).

Experimental procedures

Experiment 1

Effect of acute stress on PVN Mkp1 mRNA expression. Rats were exposed to 15 or 30 min of stress or no-stress (n=3–4). Immediately after restraint, or at the same time of day (no-stress group), rats were killed by guillotine decapitation. Brains were flash frozen in isopentane (chilled between −30 and −40 °C) and then stored at −80 °C until subsequent analysis.

Experiment 2

Effect of long-term absence of endogenous glucocorticoid (ADX) and acute stress challenge (restraint) on ACTH secretion and Mkp1 mRNA expression in the PVN, anterior pituitary, and mPFC. On the test day, ADX and sham-ADX rats were either subjected to 30 min of restraint or left in their respective home cages (2×2 between-subjects factorial design; n=6, N=24). Immediately after decapitation, brains were removed, flash frozen in isopentane (chilled between −30 and −40 °C) and then stored at −80 °C until subsequent analysis. In addition, trunk blood was collected for subsequent plasma ACTH hormone measurement.

Experiment 3

Effect of a phasic 1 or 3 h CORT pretreatment on mPFC and PVN Mkp1 mRNA expression of non-stressed adrenal-intact rats. On the test day, rats were given an injection of CORT (2.5 mg/kg, i.p.) or vehicle (1 ml/kg, i.p.) 1 or 3 h before decapitation (2×2 between-subjects factorial design; n=6; N=24). This exogenous CORT treatment procedure produces plasma CORT levels in rats that closely match the endogenous CORT levels and time course associated with a moderate intensity stressor, such as restraint (Pace et al. 2001, Barnum et al. 2008). The period of 1 to 3 h post CORT treatment is within the time range that another study detected a significant increase in mast cell Mkp1 gene expression after glucocorticoid treatment (Kassel et al. 2001). After each injection, rats were returned to their home cage and home room. In order to minimize stress-induced CORT increase in the vehicle-treated rats, we habituated rats to the injection procedure by poking rats with the blunt end of a 1 ml syringe (no needle attached) for 2 min over a 3-day period before testing. CORT was purchased from Steraloids, Inc. (Newport, RI, USA) and dissolved in vehicle (10% ethanol, 30% propylene glycol, and 60% sterile saline).

ACTH RIA

Trunk blood was collected into EDTA-containing vacutainer tubes (Becton-Dickinson, Franklin Lakes, NJ, USA), placed on wet ice, and then centrifuged for 15 min (4 °C). Plasma was then aliquoted into microfuge tubes and snap-frozen on dry ice. The blood-processing procedure was completed within 45 min after decapitation. ACTH (pg/ml) was determined in duplicate (100 μl of plasma) by using a competitive RIA protocol as described previously (Osterlund & Spencer 2011). Radiolabeled 125-I ACTH-Tracer was obtained from DiaSorin (Stillwater, MN, USA) and primary ACTH anti-serum Rb 7 (diluted to a final concentration of 1:30 000) was provided courtesy of Dr W Engeland (University of Minnesota, twin cities campus, Department of Neuroscience). The detection limit for this assay was 15 pg/ml; the intra-assay coefficient of variability was 4%.

CORT ELISA

Plasma CORT samples were measured using 20 μl of plasma with an enzyme immunoassay kit (Assay Design, Ann Arbor, MI, USA). All samples were diluted in a ratio of 1:50 in assay buffer and incubated in a 70 °C water bath for 1 h to denature corticosteroid-binding globulin. Heat-inactivated samples were then processed as per the instructions from the assay kit. Sensitivity of the CORT assay, as reported by the manufacturer, is 27 pg/ml. The intra-assay coefficient of variability was 6.3%.

In situ hybridization assay

Coronal brain sections and horizontal pituitary sections (12 μm thick) were obtained with a cryostat (model 1850; Leica Microsystems, Nussloch, Germany) and thaw mounted onto Superfrost Plus slides (Fisher Scientific, Pittsburgh, PA, USA). The 35S-UTP-labeled cRNA probes for Mkp1 mRNA were generated using a cDNA template from a portion of the Rattus norvegicus gene Dusp1 (accession number AF357203) corresponding to a 206 nucleotide mRNA sequence (positions 817–1022 from the origin) that was cloned within the Spencer lab into a transcription vector (pSCA, Agilent Technologies, Santa Clara, CA, USA). The Mkp1 cDNA-containing plasmids were subsequently linearized with the restriction endonuclease HinDIII and transcribed using T7 RNA polymerase. The identity of Mkp1 cloned DNA was verified by DNA sequencing (University of Colorado Molecular, Cellular and Developmental Biology sequencing facility). After the hybridization assay procedure (Girotti et al. 2006), slides were exposed to X-ray film (Kodak Biomax MR film) for 14 days. Semiquantitative analyses were performed on digitized images from X-ray films using the linear range of the gray values obtained from an acquisition system (Northern Lights lightbox, model B 95, Ontario, Canada; CCD camera, model XC-77, Sony, Tokyo, Japan; image capture with National Institutes of Health scion Image v1.59 software, Frederick, MD, USA), as previously described (Campeau et al. 2002). Brain regions of interest (PVN and prelimbic (PrL) and infralimbic (IL) subregions of mPFC) were identified by matching digitized rat hypothalamic structures to rat brain atlas diagrams (Paxinos et al. 1980). Quantification and analysis of images were performed by individuals that were blind to treatment condition assignments. For the PVN, bilateral measurements were taken from four tissue sections (ca. 1.8 mm posterior to bregma) for each rat (4–8 measurements for each rat brain). Measurements were also taken from 4 to 6 sections of the anterior pituitary. For the PrL and IL subregions of the mPFC, bilateral measurements were taken from 2 to 4 tissue sections (ca. 3.2 mm anterior to bregma) for each rat (4–8 measurements for each rat brain). Average uncalibrated optical densities for each region of interest were measured using the program NIH ImageJ (version 1.42q).

Statistical analysis

One-way (Experiment 1) or two-way (Experiments 2 and 3) between groups ANOVA was used to analyze the dependent measures (Statistical Package for the Social Sciences, SPSS, Macintosh computer version). Significant F-test results were followed with a Fisher's least significant difference (FLSD) post-hoc test in order to assess the statistical significance of differences between pairs of groups. Additionally, a Pearson's r correlational analysis was performed (SPSS) for Experiment 2. An alpha-level of P≤0.05 was used to determine statistical significance. All graphical presentations of data represent group means±s.e.m.

Results

Experiment 1: PVN Mkp1 mRNA increased after 15 and 30 min restraint challenge

In this first experiment, we examined whether acute psychological stress (restraint) would lead to a rapid increase in Mkp1 mRNA levels within the PVN. Under no-stress conditions, there was very little Mkp1 mRNA detected within the PVN. Restraint substantially increased PVN Mkp1 mRNA; F(3,11)=4.2, P<0.05. Post-hoc tests indicate that there was a significant increase in PVN Mkp1 mRNA within 15 min of restraint and a progressively greater increase after 30 min of restraint (Fig. 1).

Figure 1
Figure 1

Stress rapidly increased Mkp1 mRNA in the PVN. (A) Mkp1 mRNA (optical density of autoradiographs) was significantly increased after 15 min of restraint and was increased to a greater extent after 30 min of restraint. *Significant stress effect compared with the no-stress group; significant stress effect compared with 15 min stress group, P<0.05, FLSD. (B) Representative portions of autoradiographs surrounding the PVN taken from a rat within each treatment group as denoted in the aligned (A) bar graph. Mkp1 mRNA in the PVN was not detectable on basal condition autoradiographs.

Citation: Journal of Endocrinology 220, 1; 10.1530/JOE-13-0365

Experiment 2: restraint increased Mkp1 mRNA in the PVN, anterior pituitary, and PFC, and this increase in the PVN and anterior pituitary was augmented by the long-term absence of endogenous glucocorticoids (ADX)

In this second experiment, we examined whether acute stress (30 min restraint) would also lead to a rapid increase in Mkp1 mRNA in an additional anatomical element of the HPA axis (the anterior pituitary) as well as in a separate brain region (mPFC). We also examined whether a stress-induced increase in Mkp1 mRNA depended on stress-induced increases in endogenous CORT. As expected, restraint-challenged rats displayed an increase in ACTH secretion (stress effect: F(1,19)=78.3, P<0.05), and the absence of glucocorticoids resulted in a substantial increase in basal and stress-stimulated ACTH secretion (ADX effect: F(1,19)=33.8, P<0.05; Fig. 2). Plasma CORT analysis indicated that sham-ADX non-stressed rats displayed normal low-basal levels of CORT (M=48.8,±s.e.m. 16.0 ng/ml) and stressed sham-ADX rats had a significant increase in plasma CORT levels (M=464.4,±s.e.m. 21.8 ng/ml). All ADX rats had CORT levels near or below the detection threshold of the assay.

Figure 2
Figure 2

Both basal and stress-stimulated ACTH plasma levels were augmented in ADX rats. Four days after ADX or sham-ADX surgery, rats were challenged with 30 min restraint. *Significant stress effect compared with the no-stress group for the same surgical condition; significant tonic CORT condition (ADX) effect compared with the sham group for the same stress condition; P<0.05, FLSD.

Citation: Journal of Endocrinology 220, 1; 10.1530/JOE-13-0365

Under non-stressed conditions, Mkp1 mRNA levels were very low in the PVN and anterior pituitary (Fig. 3). Within the PrL and IL subregions of the mPFC, Mkp1 mRNA levels were also low, but were clearly visible on autoradiograms (Fig. 4). Sham-operated rats challenged with 30 min of restraint displayed a significant increase in Mkp1 mRNA expression within PVN (stress effect: F(1,19)=37.4, P<0.05), anterior pituitary (stress effect: F(1,19)=29.8, P<0.05), PrL cortex (stress effect: F(1,19)=14.7, P<0.05), and IL cortex (stress effect: F(1,19)=42.8, P<0.05). Stress-stimulated CORT levels of sham-operated rats were not significantly correlated with the stress-induced increase in Mkp1 mRNA levels in the PVN (r=0.27; P>0.05), PrL cortex (r=0.34; P>0.05), or IL cortex (r=−0.063; P>0.05). Interestingly, there was a trend for a negative correlation between CORT levels and stress-induced Mkp1 mRNA levels in the anterior pituitary (r=−0.64, P=0.244), suggesting that acute CORT may have had an inhibitory influence on stress-induced Mkp1 mRNA levels. Rather than attenuating stress-induced Mkp1 mRNA levels, as predicted, ADX augmented stress-stimulated Mkp1 mRNA levels within the PVN (stress×ADX interaction F(1,19)=11.0, P<0.05) and anterior pituitary (stress×ADX F(1,19)=5.1, P<0.05). There was also a trend towards higher stress-induced Mkp1 mRNA levels in the PrL and IL cortex of ADX rats; however, there was not a significant stress×ADX interaction in either brain region. On the other hand, within the IL cortex there was a significant increase in Mkp1 mRNA levels of non-stressed ADX rats compared with sham-operated rats (FLSD, P<0.05).

Figure 3
Figure 3

Stress-stimulated Mkp1 mRNA levels were augmented in PVN and anterior pituitary of ADX rats. (A) PVN and (C) anterior pituitary relative Mkp1 mRNA levels for sham-operated or ADX rats 30 min restraint challenge 4 days after surgery. *Significant stress effect compared with the no-stress group for the same surgical conditions; significant tonic CORT condition (ADX) effect compared with the sham group, for the same stress conditions; P<0.05, FLSD. Representative autoradiographs for Mkp1 mRNA expression in (B) PVN (coronal brain section) and (D) anterior pituitary (horizontal section); regions of interest are denoted on a representative autoradiograph taken from a rat from the ADX-Stress group.

Citation: Journal of Endocrinology 220, 1; 10.1530/JOE-13-0365

Figure 4
Figure 4

Stress increased Mkp1 mRNA levels to a similar degree in the mPFC of sham-operated and ADX rats. Four days after ADX or sham-ADX surgery, rats were challenged with 30 min restraint. Restraint increased Mkp1 mRNA levels in the prelimbic (PrL, A) and infralimbic (IL, B) subregions of the mPFC, and ADX increased basal Mkp1 mRNA levels in the IL. *Significant stress effect compared with the no-stress group for the same surgical condition; significant tonic CORT condition (ADX) effect compared with the sham group for the same stress condition; P<0.05, FLSD. (C) Representative autoradiographs for Mkp1 mRNA expression in mPFC (coronal brain section); regions of interest are denoted on a representative autoradiograph taken from a rat from the ADX-stress group. Note that there were low but visible Mkp1 mRNA levels in the mPFC visible on basal-condition autoradiographs.

Citation: Journal of Endocrinology 220, 1; 10.1530/JOE-13-0365

Experiment 3: acute CORT treatment was not sufficient to upregulate PVN or mPFC Mkp1 mRNA levels

Although Experiment 2 demonstrated that an increase in endogenous CORT was not necessary for a stress-induced increase in Mkp1 mRNA, there is still the possibility that an acute increase in CORT is sufficient to produce an increase in Mkp1 mRNA in PVN and mPFC, which may be masked by the effect of restraint stress. Thus, this experiment examined the effect of vehicle or CORT injection in the absence of restraint stress on subsequent Mkp1 mRNA expression. As expected, plasma CORT measures indicated that there was a greater level of plasma CORT present 1 h after CORT injection (M=149.1, ±s.e.m. 51.3 ng/ml) compared with vehicle injection (M=33.4,±s.e.m. 13.0 ng/ml). By 3 h after CORT injection, the exogenous CORT had cleared such that plasma CORT levels were low in both CORT-injected rats (M=7.5,±s.e.m. 1.5 ng/ml) and vehicle-injected rats (M=22.0,±s.e.m. 11.2 ng/ml).

We observed no difference in Mkp1 mRNA levels of CORT vs vehicle-injected rats in either brain region (Fig. 5). Similar to non-stressed conditions in Experiments 1 and 2, we observed almost undetectable levels of Mkp1 mRNA within the PVN. Within the PrL, there was a moderate level of Mkp1 mRNA expression present 1 h after injection, but it did not differ between CORT and vehicle treatments. Interestingly, for both CORT and vehicle treatment groups, there was a lower level of Mkp1 mRNA expression in PrL 3 h after injection compared with 1 h after injection (post injection time: F(1,10)=2.4, P<0.05), perhaps indicating that the stress of injection produced a transient increase in Mkp1 mRNA levels in PrL that was evident 1 h, but less so by 3 h after injection. A similar pattern of Mkp1 mRNA was observed in IL (data not shown).

Figure 5
Figure 5

Acute CORT treatment did not increase PVN or prelimbic (PrL) cortex Mkp1 mRNA levels. Adrenal-intact rats received injections of CORT (2.5 mg/kg, i.p.) or vehicle 1 3 h before they were killed. There was very low Mkp1 mRNA expression in the PVN for the four treatment groups. There was a moderately high level of Mkp1 mRNA expression in the PrL subregion of the mPFC 1 h after injection and lower levels 3 h after injection (P<0.05), but the levels did not differ between CORT or vehicle-injected rats. *Significant pretreatment-time difference effect in the PrL.

Citation: Journal of Endocrinology 220, 1; 10.1530/JOE-13-0365

Discussion

In this study, we found that Mkp1 mRNA was rapidly increased by acute psychological stress within anatomical elements of the HPA axis (PVN and anterior pituitary) and in a stress-responsive brain region that provides regulatory modulation over the HPA axis (mPFC) (Diorio et al. 1993, Radley et al. 2006, Weinberg et al. 2010). Contrary to the predictions based on studies of glucocorticoid regulation of Mkp1 gene expression in peripheral tissues and cell lines (Clark et al. 2008), we found that acute CORT treatment was not sufficient to increase Mkp1 mRNA within the brain and endocrine tissues examined. Moreover, stress-induced CORT secretion was not necessary for the rapid increase in Mkp1 mRNA observed after acute stress. Instead, we found that stress-induced Mkp1 gene expression was augmented within the PVN and anterior pituitary of the rats that lacked endogenous adrenal glucocorticoids. These results suggest that Mkp1 expression is dynamically regulated in brain and neuroendocrine tissue, and that endogenous glucocorticoids may have a tonic suppressive role in regulating Mkp1 gene expression in these tissues, perhaps by indirectly constraining activity-dependent regulation of MAP-kinase (see discussion below).

A number of studies have found that the Mkp1 gene behaves as an activity-dependent immediate early gene in response to a wide variety of stimuli within various peripheral cell types and transformed cell lines (Clark 2003, Patterson et al. 2009, Caunt & Keyse 2013). Initial indication that the Mkp1 gene may be regulated in a similar fashion within mammalian neural tissue was provided by studies that observed a rapid increase in Mkp1 mRNA in striatal and hippocampal subregions of the rodent brain after direct electrical stimulation or electroconvulsive seizure (Sgambato et al. 1998, Davis et al. 2000, Kodama et al. 2005). Subsequently, activity-dependent Mkp1 gene induction in the mammalian brain has also been observed in the suprachiasmatic nucleus in response to a light pulse during the subjective night (Doi et al. 2007). Our first experiment showed that PVN Mkp1 gene expression was rapidly increased within 15 min of restraint, an acute stress challenge that is predominantly psychological in nature (Herman & Cullinan 1997, Dayas et al. 2001). Our second experiment showed that this same stressor produced a rapid increase in Mkp1 mRNA within the anterior pituitary and mPFC (PrL and IL). Despite the contrasting influence that the PrL and IL cortex have over the PVN (inhibitory and excitatory respectively) (Radley et al. 2006), both subregions of the medial-PFC display stress-dependent rapid induction of other experience-dependent genes such as c-Fos and Fra2 (FOSL2) (Weinberg et al. 2007). We observed nearly undetectable levels of Mkp1 mRNA within the PVN and the anterior pituitary under no-stress conditions, whereas there was a greater degree of constitutive Mkp1 mRNA expression within the mPFC. Moreover, our third experiment indicates that there may be a greater sensitivity of Mkp1 mRNA induction to the mild stress of vehicle injection in the mPFC than in the PVN. Overall, our study extends the extent of known activity-dependent operation of the Mkp1 gene to neural and endocrine elements of the HPA axis and to the mPFC. In addition, our results indicate that a moderate-intensity stressor is an effective experience for producing a rapid and substantial increase in Mkp1 mRNA in the adult rat brain.

In this study, we explored the possibility that CORT serves as both an intercellular and intracellular stress-dependent signal for Mkp1 gene induction (Clark 2003, Clark et al. 2008). We found, however, that the presence of endogenous CORT was not necessary for the stress-induced increase in Mkp1 mRNA within the tissue examined. In addition, acute CORT treatment was not sufficient to increase Mkp1 mRNA levels. An in vitro study has also indicated that glucocorticoid treatment alone does not increase Mkp1 gene expression, but that study revealed that glucocorticoid treatment augmented Mkp1 gene induction in response to other cellular stimuli (Zhou et al. 2007). In contrast to the finding of that study, we observed an opposite effect. In the anatomical elements of the HPA axis there was a greater stress-induced increase in Mkp1 mRNA in rats lacking endogenous CORT. It should be noted that the mPFC, PVN, and anterior pituitary all express high levels of GR (Gustafsson et al. 1987, Herman 1993, Francis et al. 2006). Furthermore the levels of CORT typically secreted in response to restraint are sufficient to activate GR in those tissues (Reul & de Kloet 1985, Spencer 1993). Thus, we conclude that CORT-activated GR does not contribute to a rapid induction of Mkp1 mRNA in the PVN, mPFC, and anterior pituitary.

Several functional glucocorticoid response elements (GREs) have recently been identified in the distal promoter region of the human Mkp1 gene (Shipp et al. 2010, Tchen et al. 2010). Although some of those putative GREs exhibit high homologous nucleotide sequences at approximately the same upstream locations as for the rat Mkp1 gene, they fail to exhibit similar functional responsiveness to glucocorticoids when assessed in gene transcription reporter assays (Tchen et al. 2010). Whether glucocorticoids influence transcriptional processes is often dependent on cellular function and location. For example, glucocorticoids provide suppressive transcriptional regulation of the Crh gene in the PVN CRH neuroendocrine neurons (Swanson & Simmons 1989, Ginsberg et al. 2003, Bali et al. 2008, Sharma et al. 2013), but in other forebrain regions, such as the amygdala and bed nucleus of the stria terminalis, glucocorticoids either upregulate Crh gene expression or have no effect (Makino et al. 1995, Schulkin et al. 1998). Glucocorticoid regulation of the Mkp1 gene may also vary with cell phenotype and cell state, and these factors may differ across species (Tchen et al. 2010).

The profile of glucocorticoid regulation of Mkp1 gene expression in the PVN that we observed in this study is similar to what we have seen in previous studies for the immediate early genes c-Fos, Zif268 and Ngfi-b (Girotti et al. 2007, Pace et al. 2009). Whereas the absence of endogenous glucocorticoids produced a large increase in both basal and stimulated ACTH hormone levels, for each of these immediate early genes only stimulated levels were augmented in the PVN of ADX rats. This expression profile may indicate that glucocorticoids indirectly regulate the expression of Mkp1 and other immediate early genes within the PVN. One possible mechanism for this indirect effect could be alteration of CRH neuron responses to acute stress by altering CRH receptor (CRH-R1) expression within PVN CRH neurons (Luo et al. 1995, Imaki et al. 2001). For example, ADX has been shown to increase CRH-R1 expression in the rat PVN (Luo et al. 1995). Thus, the long-term absence of CORT may lead to an augmented positive CRH feedback loop onto PVN CRH neurons, resulting in increased signaling activity (e.g., MAP-kinase activation), transcriptional processes (e.g., Mkp1 gene expression), and neuropeptide release (e.g., CRH) within these neuroendocrine cells. Regardless of the mechanism, there appears to be some process by which the tonic presence of glucocorticoids constrains the general reactivity of these cells to excitation (Pace et al. 2009, Osterlund & Spencer 2011, Osterlund et al. 2011, Weiser et al. 2011).

Although the specific process remains undetermined, the augmented Mkp1 gene expression in the absence of glucocorticoids may be secondary to an augmentation of ERK1/2 activation in CRH neurons. We have previously observed an increased number of stress-induced phospho-ERK1/2-positive cells in the PVN of ADX rats, which was normalized by giving ADX rats CORT in their drinking water (Osterlund et al. 2011). MAP-kinase pathway activation has been found to converge on Mkp1 gene expression in a number of cell types (Brondello et al. 1997, Camps et al. 2000, Kassel et al. 2001). This Mkp1 gene induction may serve as a form of intracellular negative feedback control over the pluripotent MAP-kinase intracellular signaling network. There is some evidence that in the neural tissue the activity-dependent Mkp1 gene induction depends specifically on ERK1/2 (Sgambato et al. 1998, Jeanneteau et al. 2012). Interestingly, in cultured cortical neurons, ERK1/2 activation was necessary for activity-dependent Mkp1 gene induction, with the subsequent upregulated MKP1 protein responsible for negative regulation of the phosphorylation state and function of a different MAP-kinase (c-jun N-terminal kinase) (Jeanneteau et al. 2012). Basal CORT levels may not only constrain Mkp1 expression within the HPA axis, they may also have an important modulatory influence on Mkp1 gene expression in a variety of extrinsic hypothalamic forebrain regions. In this study, we saw a trend towards greater stress-induced Mkp1 mRNA in the mPFC of ADX rats. In addition, there was a significant increase in basal Mkp1 mRNA in the IL subregion of the mPFC of ADX rats.

Our results, taken together with others, indicate that the Mkp1 gene may be induced in a wide-range of brain regions by an extensive set of experiential conditions. Thus, the activity dependence of Mkp1 gene expression may resemble that of some other activity-dependent immediate early genes, such as c-Fos, Zif268, and Arc, which are critical for experience-dependent neuroplasticity (Guzowski et al. 2001, Loebrich & Nedivi 2009, Okuno 2011). Given the importance of the MAP-kinase intracellular signaling network for neuroplasticity in the developing and adult brain, it would not be surprising that tight regulation of this molecular network is critical for optimal function (Sweatt 2001, Waltereit & Weller 2003, Davis & Laroche 2006, Ayroldi et al. 2012). Mice lacking the Mkp1 gene exhibit a range of heightened inflammatory processes, presumably due to the overactivity of MAP-kinases (Chi et al. 2006, Maier et al. 2007, Wang et al. 2008, Patterson et al. 2009, Vandevyver et al. 2012). This anti-inflammatory role of MKP1 may extend to brain microglia (Zhou et al. 2007). Cortical neurons cultured from Mkp1 gene-knockout mice are deficient in their axonal branching response to brain-derived neurotrophic factor (Jeanneteau et al. 2012). Support for the importance of MKP1 gene expression levels in human brain function is provided by a study that found increased Mkp1 mRNA levels in the postmortem brains of individuals with major depressive disorder (Duric et al. 2010). The dynamic interaction between MAP-kinases and MKP1 appears to be an important element of neural function, and may be an effective pharmacotherapeutic target. Further study of how that interaction may be modulated by the tonic changes in glucocorticoids associated with chronic stress and various mental and physical disorders is warranted.

Declaration of interest

The authors declared no conflict of interest that could be perceived as prejudicial to the impartiality of the research reported.

Funding

This work was supported by grants MH75968 and MH065977 from the National Institute of Mental Health (NIH) and by the University of Colorado Undergraduate Research Opportunity Program.

Acknowledgements

We thank Erin Jarvis for providing technical assistance with the cloning of rat Mkp1 cDNA.

References

  • AyroldiECannarileLMiglioratiGNocentiniGDelfinoDVRiccardiC2012Mechanisms of the anti-inflammatory effects of glucocorticoids: genomic and nongenomic interference with MAPK signaling pathways. FASEB Journal2648054820. (doi:10.1096/fj.12-216382)

    • Search Google Scholar
    • Export Citation
  • BaliBFerencziSKovácsKJ2008Direct inhibitory effect of glucocorticoids on corticotrophin-releasing hormone gene expression in neurones of the paraventricular nucleus in rat hypothalamic organotypic cultures. Journal of Neuroendocrinology2010451051. (doi:10.1111/j.1365-2826.2008.01759.x)

    • Search Google Scholar
    • Export Citation
  • BarnumCJEskowKLDupreKBlandinoPDeakTBishopC2008Exogenous corticosterone reduces l-DOPA-induced dyskinesia in the hemi-Parkinsonian rat: role for interleukin-1β. Neuroscience1563041. (doi:10.1016/j.neuroscience.2008.07.016)

    • Search Google Scholar
    • Export Citation
  • BrondelloJMBrunetAPouysségurJMcKenzieFR1997The dual specificity mitogen-activated protein kinase phosphatase-1 and -2 are induced by the p42/p44MAPK cascade. Journal of Biological Chemistry27213681376. (doi:10.1074/jbc.272.2.1368)

    • Search Google Scholar
    • Export Citation
  • BurkeSJGoffMRUpdegraffBLLuDBrownPLMinkinSCBiggerstaffJPZhaoLKarlstadMDCollierJJ2012Regulation of the CCL2 gene in pancreatic β-cells by IL-1β and glucocorticoids: role of MKP-1. PLoS ONE7e46986. (doi:10.1371/journal.pone.0046986)

    • Search Google Scholar
    • Export Citation
  • CampeauSDolanDAkilHWatsonSJ2002c-fos mRNA induction in acute and chronic audiogenic stress: possible role of the orbitofrontal cortex in habituation. Stress5121130. (doi:10.1080/10253890290027895)

    • Search Google Scholar
    • Export Citation
  • CampsMNicholsAArkinstallS2000Dual specificity phosphatases: a gene family for control of MAP kinase function. FASEB Journal14616.

  • CauntCJKeyseSM2013Dual-specificity MAP kinase phosphatases (MKPs): shaping the outcome of MAP kinase signalling. FEBS Journal280489504. (doi:10.1111/j.1742-4658.2012.08716.x)

    • Search Google Scholar
    • Export Citation
  • ChiHBarrySPRothRJWuJJJonesEABennettAMFlavellRA2006Dynamic regulation of pro- and anti-inflammatory cytokines by MAPK phosphatase 1 (MKP-1) in innate immune responses. PNAS10322742279. (doi:10.1073/pnas.0510965103)

    • Search Google Scholar
    • Export Citation
  • ClarkAR2003MAP kinase phosphatase 1: a novel mediator of biological effects of glucocorticoids?Journal of Endocrinology178512. (doi:10.1677/joe.0.1780005)

    • Search Google Scholar
    • Export Citation
  • ClarkARMartinsJRSTchenCR2008Role of dual specificity phosphatases in biological responses to glucocorticoids. Journal of Biological Chemistry2832576525769. (doi:10.1074/jbc.R700053200)

    • Search Google Scholar
    • Export Citation
  • DallmanMFAkanaSFCascioCSDarlingtonDNJacobsonLLevinN1987Regulation of ACTH secretion: variations on a theme of B. Recent Progress in Hormone Research43113173.

    • Search Google Scholar
    • Export Citation
  • DavisSLarocheS2006Mitogen-activated protein kinase/extracellular regulated kinase signalling and memory stabilization: a review. Genes Brain and Behavior5 (Suppl 2) 6172. (doi:10.1111/j.1601-183X.2006.00230.x)

    • Search Google Scholar
    • Export Citation
  • DavisSVanhouttePPagèsCCabocheJLarocheS2000The MAPK/ERK cascade targets both Elk-1 and cAMP response element-binding protein to control long-term potentiation-dependent gene expression in the dentate gyrus in vivo. Journal of Neuroscience2045634572.

    • Search Google Scholar
    • Export Citation
  • DayasCVBullerKMCraneJWXuYDayTA2001Stressor categorization: acute physical and psychological stressors elicit distinctive recruitment patterns in the amygdala and in medullary noradrenergic cell groups. European Journal of Neuroscience1411431152. (doi:10.1046/j.0953-816x.2001.01733.x)

    • Search Google Scholar
    • Export Citation
  • DiorioDViauVMeaneyMJ1993The role of the medial prefrontal cortex (cingulate gyrus) in the regulation of hypothalamic–pituitary–adrenal responses to stress. Journal of Neuroscience1338393847.

    • Search Google Scholar
    • Export Citation
  • DoiMChoSYujnovskyIHirayamaJCermakianNCatoACBSassone-CorsiP2007Light-inducible and clock-controlled expression of MAP kinase phosphatase 1 in mouse central pacemaker neurons. Journal of Biological Rhythms22127139. (doi:10.1177/0748730406298332)

    • Search Google Scholar
    • Export Citation
  • DuricVBanasrMLicznerskiPSchmidtHDStockmeierCASimenAANewtonSSDumanRS2010A negative regulator of MAP kinase causes depressive behavior. Nature Medicine1613281332. (doi:10.1038/nm.2219)

    • Search Google Scholar
    • Export Citation
  • FrancisABPaceTWWGinsbergABRubinBASpencerRL2006Limited brain diffusion of the glucocorticoid receptor agonist RU28362 following i.c.v. administration: implications for i.c.v. drug delivery and glucocorticoid negative feedback in the hypothalamic–pituitary–adrenal axis. Neuroscience14115031515. (doi:10.1016/j.neuroscience.2006.04.067)

    • Search Google Scholar
    • Export Citation
  • GinsbergABCampeauSDayHESpencerRL2003Acute glucocorticoid pretreatment suppresses stress-induced hypothalamic–pituitary–adrenal axis hormone secretion and expression of corticotropin-releasing hormone hnRNA but does not affect c-fos mRNA or fos protein expression in the paraventricular nucleus of the hypothalamus. Journal of Neuroendocrinology1510751083. (doi:10.1046/j.1365-2826.2003.01100.x)

    • Search Google Scholar
    • Export Citation
  • GirottiMPaceTWWGaylordRIRubinBAHermanJPSpencerRL2006Habituation to repeated restraint stress is associated with lack of stress-induced c-fos expression in primary sensory processing areas of the rat brain. Neuroscience13810671081. (doi:10.1016/j.neuroscience.2005.12.002)

    • Search Google Scholar
    • Export Citation
  • GirottiMWeinbergMSSpencerRL2007Differential responses of hypothalamus–pituitary–adrenal axis immediate early genes to corticosterone and circadian drive. Endocrinology14825422552. (doi:10.1210/en.2006-1304)

    • Search Google Scholar
    • Export Citation
  • GrewalSSYorkRDStorkPJ1999Extracellular-signal-regulated kinase signalling in neurons. Current Opinion in Neurobiology9544553. (doi:10.1016/S0959-4388(99)00010-0)

    • Search Google Scholar
    • Export Citation
  • GustafssonJACarlstedt-DukeJPoellingerLOkretSWikströmACBrönnegårdMGillnerMDongYFuxeKCintraA1987Biochemistry, molecular biology, and physiology of the glucocorticoid receptor. Endocrine Reviews8185234. (doi:10.1210/edrv-8-2-185)

    • Search Google Scholar
    • Export Citation
  • GuzowskiJFSetlowBWagnerEKMcGaughJL2001Experience-dependent gene expression in the rat hippocampus after spatial learning: a comparison of the immediate-early genes. Arc c-fos and zif268 Journal of Neuroscience2150895098.

    • Search Google Scholar
    • Export Citation
  • HermanJP1993Regulation of adrenocorticosteroid receptor mRNA expression in the central nervous system. Cellular and Molecular Neurobiology13349372. (doi:10.1007/BF00711577)

    • Search Google Scholar
    • Export Citation
  • HermanJPCullinanWE1997Neurocircuitry of stress: central control of the hypothalamo-pituitary–adrenocortical axis. Trends in Neurosciences207884. (doi:10.1016/S0166-2236(96)10069-2)

    • Search Google Scholar
    • Export Citation
  • ImakiTKatsumataHMiyataMNaruseMImakiJMinamiS2001Expression of corticotropin-releasing hormone type 1 receptor in paraventricular nucleus after acute stress. Neuroendocrinology73293301. (doi:10.1159/000054646)

    • Search Google Scholar
    • Export Citation
  • IssaRXieSKhorasaniNSukkarMAdcockIMLeeK-YChungKF2007Corticosteroid inhibition of growth-related oncogene protein-α via mitogen-activated kinase phosphatase-1 in airway smooth muscle cells. Journal of Immunology17873667375.

    • Search Google Scholar
    • Export Citation
  • JeanneteauFDLambertWMIsmailiNBathKGLeeFSGarabedianMJChaoMV2012BDNF and glucocorticoids regulate corticotrophin-releasing hormone (CRH) homeostasis in the hypothalamus. PNAS10913051310. (doi:10.1073/pnas.1114122109)

    • Search Google Scholar
    • Export Citation
  • KasselOSanconoAKrätzschmarJKreftBStassenMCatoAC2001Glucocorticoids inhibit MAP kinase via increased expression and decreased degradation of MKP-1. EMBO Journal2071087116. (doi:10.1093/emboj/20.24.7108)

    • Search Google Scholar
    • Export Citation
  • KeyseSM2000Protein phosphatases and the regulation of mitogen-activated protein kinase signalling. Current Opinion in Cell Biology12186192. (doi:10.1016/S0955-0674(99)00075-7)

    • Search Google Scholar
    • Export Citation
  • KhanAMWattsAG2004Intravenous 2-deoxy-d-glucose injection rapidly elevates levels of the phosphorylated forms of p44/42 mitogen-activated protein kinases (extracellularly regulated kinases 1/2) in rat hypothalamic parvicellular paraventricular neurons. Endocrinology145351359. (doi:10.1210/en.2003-0539)

    • Search Google Scholar
    • Export Citation
  • KhanAMPonzioTASanchez-WattsGStanleyBGHattonGIWattsAG2007Catecholaminergic control of mitogen-activated protein kinase signaling in paraventricular neuroendocrine neurons in vivo and in vitro: a proposed role during glycemic challenges. Journal of Neuroscience2773447360. (doi:10.1523/JNEUROSCI.0873-07.2007)

    • Search Google Scholar
    • Export Citation
  • KhanAMKaminskiKLSanchez-WattsGPonzioTAKuzmiskiJBBainsJSWattsAG2011MAP kinases couple hindbrain-derived catecholamine signals to hypothalamic adrenocortical control mechanisms during glycemia-related challenges. Journal of Neuroscience311847918491. (doi:10.1523/JNEUROSCI.4785-11.2011)

    • Search Google Scholar
    • Export Citation
  • KodamaMRussellDSDumanRS2005Electroconvulsive seizures increase the expression of MAP kinase phosphatases in limbic regions of rat brain. Neuropsychopharmacology30360371. (doi:10.1038/sj.npp.1300588)

    • Search Google Scholar
    • Export Citation
  • KomatsuKJonoHLimJHImasatoAXuHKaiHYanCLiJ-D2008Glucocorticoids inhibit nontypeable Haemophilus influenzae-induced MUC5AC mucin expression via MAPK phosphatase-1-dependent inhibition of p38 MAPK. Biochemical and Biophysical Research Communications377763768. (doi:10.1016/j.bbrc.2008.10.091)

    • Search Google Scholar
    • Export Citation
  • KovácsKJSawchenkoPE1996Sequence of stress-induced alterations in indices of synaptic and transcriptional activation in parvocellular neurosecretory neurons. Journal of Neuroscience16262273.

    • Search Google Scholar
    • Export Citation
  • LoebrichSNediviE2009The function of activity-regulated genes in the nervous system. Physiological Reviews8910791103. (doi:10.1152/physrev.00013.2009)

    • Search Google Scholar
    • Export Citation
  • LuoXKissARabadan-DiehlCAguileraG1995Regulation of hypothalamic and pituitary corticotropin-releasing hormone receptor messenger ribonucleic acid by adrenalectomy and glucocorticoids. Endocrinology13638773883. (doi:10.1210/en.136.9.3877)

    • Search Google Scholar
    • Export Citation
  • MaierJVBremaSTuckermannJHerzerUKleinMStassenMMoorthyACatoACB2007Dual specificity phosphatase 1 knockout mice show enhanced susceptibility to anaphylaxis but are sensitive to glucocorticoids. Molecular Endocrinology2126632671. (doi:10.1210/me.2007-0067)

    • Search Google Scholar
    • Export Citation
  • MakinoSSchulkinJSmithMAPacákKPalkovitsMGoldPW1995Regulation of corticotropin-releasing hormone receptor messenger ribonucleic acid in the rat brain and pituitary by glucocorticoids and stress. Endocrinology13645174525. (doi:10.1210/en.136.10.4517)

    • Search Google Scholar
    • Export Citation
  • Nicoletti-CarvalhoJELellis-SantosCYamanakaTSNogueiraTCCaperutoLCLeiteARAnhêGFBordinS2010MKP-1 mediates glucocorticoid-induced ERK1/2 dephosphorylation and reduction in pancreatic β-cell proliferation in islets from early lactating mothers. American Journal of Physiology. Endocrinology and Metabolism299E1006E1015. (doi:10.1152/ajpendo.00341.2010)

    • Search Google Scholar
    • Export Citation
  • OkunoH2011Regulation and function of immediate-early genes in the brain: beyond neuronal activity markers. Neuroscience Research69175186. (doi:10.1016/j.neures.2010.12.007)

    • Search Google Scholar
    • Export Citation
  • OsterlundCSpencerR2011Corticosterone pretreatment suppresses stress-induced hypothalamic–pituitary–adrenal axis activity via multiple actions that vary with time, site of action, and de novo protein synthesis. Journal of Endocrinology208311322. (doi:10.1530/JOE-10-0413)

    • Search Google Scholar
    • Export Citation
  • OsterlundCDJarvisEChadayammuriAUnnithanRWeiserMJSpencerRL2011Tonic, but not phasic corticosterone, constrains stress activated extracellular-regulated-kinase 1/ 2 immunoreactivity within the hypothalamic paraventricular nucleus. Journal of Neuroendocrinology2312411251. (doi:10.1111/j.1365-2826.2011.02220.x)

    • Search Google Scholar
    • Export Citation
  • PaceTColeMWardGKalmanBSpencerR2001Acute exposure to a novel stressor further reduces the habituated corticosterone response to restraint in rats. Stress4319331. (doi:10.3109/10253890109014755)

    • Search Google Scholar
    • Export Citation
  • PaceTWWGaylordRTopczewskiFGirottiMRubinBSpencerRL2005Immediate-early gene induction in hippocampus and cortex as a result of novel experience is not directly related to the stressfulness of that experience. European Journal of Neuroscience2216791690. (doi:10.1111/j.1460-9568.2005.04354.x)

    • Search Google Scholar
    • Export Citation
  • PaceTWWGaylordRIJarvisEGirottiMSpencerRL2009Differential glucocorticoid effects on stress-induced gene expression in the paraventricular nucleus of the hypothalamus and ACTH secretion in the rat. Stress12400411. (doi:10.1080/10253890802530730)

    • Search Google Scholar
    • Export Citation
  • PattersonKIBrummerTO'BrienPMDalyRJ2009Dual-specificity phosphatases: critical regulators with diverse cellular targets. Biochemical Journal418475489. (doi:10.1042/BJ20082234)

    • Search Google Scholar
    • Export Citation
  • PaxinosGWatsonCREmsonPC1980AChE-stained horizontal sections of the rat brain in stereotaxic coordinates. Journal of Neuroscience Methods3129149. (doi:10.1016/0165-0270(80)90021-7)

    • Search Google Scholar
    • Export Citation
  • RadleyJJAriasCMSawchenkoPE2006Regional differentiation of the medial prefrontal cortex in regulating adaptive responses to acute emotional stress. Journal of Neuroscience261296712976. (doi:10.1523/JNEUROSCI.4297-06.2006)

    • Search Google Scholar
    • Export Citation
  • ReulJMde KloetER1985Two receptor systems for corticosterone in rat brain: microdistribution and differential occupation. Endocrinology11725052511. (doi:10.1210/endo-117-6-2505)

    • Search Google Scholar
    • Export Citation
  • SawchenkoPEBrownERChanRKEricssonALiHYRolandBLKovácsKJ1996The paraventricular nucleus of the hypothalamus and the functional neuroanatomy of visceromotor responses to stress. Progress in Brain Research107201222.

    • Search Google Scholar
    • Export Citation
  • SchulkinJGoldPWMcEwenBS1998Induction of corticotropin-releasing hormone gene expression by glucocorticoids: implication for understanding the states of fear and anxiety and allostatic load. Psychoneuroendocrinology23219243. (doi:10.1016/S0306-4530(97)00099-1)

    • Search Google Scholar
    • Export Citation
  • SgambatoVPagèsCRogardMBessonMJCabocheJ1998Extracellular signal-regulated kinase (ERK) controls immediate early gene induction on corticostriatal stimulation. Journal of Neuroscience1888148825.

    • Search Google Scholar
    • Export Citation
  • SharmaDBhaveSGreggEUhtR2013Dexamethasone induces a putative repressor complex and chromatin modifications in the CRH promoter. Molecular Endocrinology2711421152. (doi:10.1210/me.2013-1079)

    • Search Google Scholar
    • Export Citation
  • ShippLELeeJVYuC-YPufallMZhangPScottDKWangJ-C2010Transcriptional regulation of human dual specificity protein phosphatase 1 (DUSP1) gene by glucocorticoids. PLoS ONE5e13754. (doi:10.1371/journal.pone.0013754)

    • Search Google Scholar
    • Export Citation
  • ShipstonMJ1995Mechanism(s) of early glucocorticoid inhibition of adrenocorticotropin secretion from anterior pituitary corticotropes. Trends in Endocrinology and Metabolism6261266. (doi:10.1016/1043-2760(95)00149-2)

    • Search Google Scholar
    • Export Citation
  • SpencerRL1993Diurnal differences in basal and acute stress levels of type I and type II adrenal steroid receptor activation in neural and immune tissues. Endocrinology13319411950. (doi:10.1210/en.133.5.1941)

    • Search Google Scholar
    • Export Citation
  • SunHCharlesCHLauLFTonksNK1993MKP-1 (3CH134), an immediate early gene product, is a dual specificity phosphatase that dephosphorylates MAP kinase in vivo. Cell75487493. (doi:10.1016/0092-8674(93)90383-2)

    • Search Google Scholar
    • Export Citation
  • SwansonLWSimmonsDM1989Differential steroid hormone and neural influences on peptide mRNA levels in CRH cells of the paraventricular nucleus: a hybridization histochemical study in the rat. Journal of Comparative Neurology285413435. (doi:10.1002/cne.902850402)

    • Search Google Scholar
    • Export Citation
  • SweattJD2001The neuronal MAP kinase cascade: a biochemical signal integration system subserving synaptic plasticity and memory. Journal of Neurochemistry76110. (doi:10.1046/j.1471-4159.2001.00054.x)

    • Search Google Scholar
    • Export Citation
  • TchenCRMartinsJRSPaktiawalNPerelliRSaklatvalaJClarkAR2010Glucocorticoid regulation of mouse and human dual specificity phosphatase 1 (DUSP1) genes: unusual cis-acting elements and unexpected evolutionary divergence. Journal of Biological Chemistry28526422652. (doi:10.1074/jbc.M109.037309)

    • Search Google Scholar
    • Export Citation
  • TheodosiouAAshworthA2002MAP kinase phosphatases. Genome Biology3REVIEWS3009. (doi:10.1186/gb-2002-3-7-reviews3009)

  • VandevyverSDejagerLVan BogaertTKleymanALiuYTuckermannJLibertC2012Glucocorticoid receptor dimerization induces MKP1 to protect against TNF-induced inflammation. Journal of Clinical Investigation12221302140. (doi:10.1172/JCI60006)

    • Search Google Scholar
    • Export Citation
  • WaltereitRWellerM2003Signaling from cAMP/PKA to MAPK and synaptic plasticity. Molecular Neurobiology2799106. (doi:10.1385/MN:27:1:99)

    • Search Google Scholar
    • Export Citation
  • WangXNelinLDKuhlmanJRMengXWeltySELiuY2008The role of MAP kinase phosphatase-1 in the protective mechanism of dexamethasone against endotoxemia. Life Sciences83671680. (doi:10.1016/j.lfs.2008.09.003)

    • Search Google Scholar
    • Export Citation
  • WattsAG2005Glucocorticoid regulation of peptide genes in neuroendocrine CRH neurons: a complexity beyond negative feedback. Frontiers in Neuroendocrinology26109130. (doi:10.1016/j.yfrne.2005.09.001)

    • Search Google Scholar
    • Export Citation
  • WeinbergMGirottiMSpencerR2007Restraint-induced fra-2 and c-fos expression in the rat forebrain: relationship to stress duration. Neuroscience150478486. (doi:10.1016/j.neuroscience.2007.09.013)

    • Search Google Scholar
    • Export Citation
  • WeinbergMSJohnsonDCBhattAPSpencerRL2010Medial prefrontal cortex activity can disrupt the expression of stress response habituation. Neuroscience168744756. (doi:10.1016/j.neuroscience.2010.04.006)

    • Search Google Scholar
    • Export Citation
  • WeiserMJOsterlundCSpencerRL2011Inhibitory effects of corticosterone in the hypothalamic paraventricular nucleus (PVN) on stress-induced adrenocorticotrophic hormone secretion and gene expression in the PVN and anterior pituitary. Journal of Neuroendocrinology2312311240. (doi:10.1111/j.1365-2826.2011.02217.x)

    • Search Google Scholar
    • Export Citation
  • ZhouYLingE-ADheenST2007Dexamethasone suppresses monocyte chemoattractant protein-1 production via mitogen activated protein kinase phosphatase-1 dependent inhibition of Jun N-terminal kinase and p38 mitogen-activated protein kinase in activated rat microglia. Journal of Neurochemistry102667678. (doi:10.1111/j.1471-4159.2007.04535.x)

    • Search Google Scholar
    • Export Citation

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    Stress rapidly increased Mkp1 mRNA in the PVN. (A) Mkp1 mRNA (optical density of autoradiographs) was significantly increased after 15 min of restraint and was increased to a greater extent after 30 min of restraint. *Significant stress effect compared with the no-stress group; significant stress effect compared with 15 min stress group, P<0.05, FLSD. (B) Representative portions of autoradiographs surrounding the PVN taken from a rat within each treatment group as denoted in the aligned (A) bar graph. Mkp1 mRNA in the PVN was not detectable on basal condition autoradiographs.

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    Both basal and stress-stimulated ACTH plasma levels were augmented in ADX rats. Four days after ADX or sham-ADX surgery, rats were challenged with 30 min restraint. *Significant stress effect compared with the no-stress group for the same surgical condition; significant tonic CORT condition (ADX) effect compared with the sham group for the same stress condition; P<0.05, FLSD.

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    Stress-stimulated Mkp1 mRNA levels were augmented in PVN and anterior pituitary of ADX rats. (A) PVN and (C) anterior pituitary relative Mkp1 mRNA levels for sham-operated or ADX rats 30 min restraint challenge 4 days after surgery. *Significant stress effect compared with the no-stress group for the same surgical conditions; significant tonic CORT condition (ADX) effect compared with the sham group, for the same stress conditions; P<0.05, FLSD. Representative autoradiographs for Mkp1 mRNA expression in (B) PVN (coronal brain section) and (D) anterior pituitary (horizontal section); regions of interest are denoted on a representative autoradiograph taken from a rat from the ADX-Stress group.

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    Stress increased Mkp1 mRNA levels to a similar degree in the mPFC of sham-operated and ADX rats. Four days after ADX or sham-ADX surgery, rats were challenged with 30 min restraint. Restraint increased Mkp1 mRNA levels in the prelimbic (PrL, A) and infralimbic (IL, B) subregions of the mPFC, and ADX increased basal Mkp1 mRNA levels in the IL. *Significant stress effect compared with the no-stress group for the same surgical condition; significant tonic CORT condition (ADX) effect compared with the sham group for the same stress condition; P<0.05, FLSD. (C) Representative autoradiographs for Mkp1 mRNA expression in mPFC (coronal brain section); regions of interest are denoted on a representative autoradiograph taken from a rat from the ADX-stress group. Note that there were low but visible Mkp1 mRNA levels in the mPFC visible on basal-condition autoradiographs.

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    Acute CORT treatment did not increase PVN or prelimbic (PrL) cortex Mkp1 mRNA levels. Adrenal-intact rats received injections of CORT (2.5 mg/kg, i.p.) or vehicle 1 3 h before they were killed. There was very low Mkp1 mRNA expression in the PVN for the four treatment groups. There was a moderately high level of Mkp1 mRNA expression in the PrL subregion of the mPFC 1 h after injection and lower levels 3 h after injection (P<0.05), but the levels did not differ between CORT or vehicle-injected rats. *Significant pretreatment-time difference effect in the PrL.

  • AyroldiECannarileLMiglioratiGNocentiniGDelfinoDVRiccardiC2012Mechanisms of the anti-inflammatory effects of glucocorticoids: genomic and nongenomic interference with MAPK signaling pathways. FASEB Journal2648054820. (doi:10.1096/fj.12-216382)

    • Search Google Scholar
    • Export Citation
  • BaliBFerencziSKovácsKJ2008Direct inhibitory effect of glucocorticoids on corticotrophin-releasing hormone gene expression in neurones of the paraventricular nucleus in rat hypothalamic organotypic cultures. Journal of Neuroendocrinology2010451051. (doi:10.1111/j.1365-2826.2008.01759.x)

    • Search Google Scholar
    • Export Citation
  • BarnumCJEskowKLDupreKBlandinoPDeakTBishopC2008Exogenous corticosterone reduces l-DOPA-induced dyskinesia in the hemi-Parkinsonian rat: role for interleukin-1β. Neuroscience1563041. (doi:10.1016/j.neuroscience.2008.07.016)

    • Search Google Scholar
    • Export Citation
  • BrondelloJMBrunetAPouysségurJMcKenzieFR1997The dual specificity mitogen-activated protein kinase phosphatase-1 and -2 are induced by the p42/p44MAPK cascade. Journal of Biological Chemistry27213681376. (doi:10.1074/jbc.272.2.1368)

    • Search Google Scholar
    • Export Citation
  • BurkeSJGoffMRUpdegraffBLLuDBrownPLMinkinSCBiggerstaffJPZhaoLKarlstadMDCollierJJ2012Regulation of the CCL2 gene in pancreatic β-cells by IL-1β and glucocorticoids: role of MKP-1. PLoS ONE7e46986. (doi:10.1371/journal.pone.0046986)

    • Search Google Scholar
    • Export Citation
  • CampeauSDolanDAkilHWatsonSJ2002c-fos mRNA induction in acute and chronic audiogenic stress: possible role of the orbitofrontal cortex in habituation. Stress5121130. (doi:10.1080/10253890290027895)

    • Search Google Scholar
    • Export Citation
  • CampsMNicholsAArkinstallS2000Dual specificity phosphatases: a gene family for control of MAP kinase function. FASEB Journal14616.

  • CauntCJKeyseSM2013Dual-specificity MAP kinase phosphatases (MKPs): shaping the outcome of MAP kinase signalling. FEBS Journal280489504. (doi:10.1111/j.1742-4658.2012.08716.x)

    • Search Google Scholar
    • Export Citation
  • ChiHBarrySPRothRJWuJJJonesEABennettAMFlavellRA2006Dynamic regulation of pro- and anti-inflammatory cytokines by MAPK phosphatase 1 (MKP-1) in innate immune responses. PNAS10322742279. (doi:10.1073/pnas.0510965103)

    • Search Google Scholar
    • Export Citation
  • ClarkAR2003MAP kinase phosphatase 1: a novel mediator of biological effects of glucocorticoids?Journal of Endocrinology178512. (doi:10.1677/joe.0.1780005)

    • Search Google Scholar
    • Export Citation
  • ClarkARMartinsJRSTchenCR2008Role of dual specificity phosphatases in biological responses to glucocorticoids. Journal of Biological Chemistry2832576525769. (doi:10.1074/jbc.R700053200)

    • Search Google Scholar
    • Export Citation
  • DallmanMFAkanaSFCascioCSDarlingtonDNJacobsonLLevinN1987Regulation of ACTH secretion: variations on a theme of B. Recent Progress in Hormone Research43113173.

    • Search Google Scholar
    • Export Citation
  • DavisSLarocheS2006Mitogen-activated protein kinase/extracellular regulated kinase signalling and memory stabilization: a review. Genes Brain and Behavior5 (Suppl 2) 6172. (doi:10.1111/j.1601-183X.2006.00230.x)

    • Search Google Scholar
    • Export Citation
  • DavisSVanhouttePPagèsCCabocheJLarocheS2000The MAPK/ERK cascade targets both Elk-1 and cAMP response element-binding protein to control long-term potentiation-dependent gene expression in the dentate gyrus in vivo. Journal of Neuroscience2045634572.

    • Search Google Scholar
    • Export Citation
  • DayasCVBullerKMCraneJWXuYDayTA2001Stressor categorization: acute physical and psychological stressors elicit distinctive recruitment patterns in the amygdala and in medullary noradrenergic cell groups. European Journal of Neuroscience1411431152. (doi:10.1046/j.0953-816x.2001.01733.x)

    • Search Google Scholar
    • Export Citation
  • DiorioDViauVMeaneyMJ1993The role of the medial prefrontal cortex (cingulate gyrus) in the regulation of hypothalamic–pituitary–adrenal responses to stress. Journal of Neuroscience1338393847.

    • Search Google Scholar
    • Export Citation
  • DoiMChoSYujnovskyIHirayamaJCermakianNCatoACBSassone-CorsiP2007Light-inducible and clock-controlled expression of MAP kinase phosphatase 1 in mouse central pacemaker neurons. Journal of Biological Rhythms22127139. (doi:10.1177/0748730406298332)

    • Search Google Scholar
    • Export Citation
  • DuricVBanasrMLicznerskiPSchmidtHDStockmeierCASimenAANewtonSSDumanRS2010A negative regulator of MAP kinase causes depressive behavior. Nature Medicine1613281332. (doi:10.1038/nm.2219)

    • Search Google Scholar
    • Export Citation
  • FrancisABPaceTWWGinsbergABRubinBASpencerRL2006Limited brain diffusion of the glucocorticoid receptor agonist RU28362 following i.c.v. administration: implications for i.c.v. drug delivery and glucocorticoid negative feedback in the hypothalamic–pituitary–adrenal axis. Neuroscience14115031515. (doi:10.1016/j.neuroscience.2006.04.067)

    • Search Google Scholar
    • Export Citation
  • GinsbergABCampeauSDayHESpencerRL2003Acute glucocorticoid pretreatment suppresses stress-induced hypothalamic–pituitary–adrenal axis hormone secretion and expression of corticotropin-releasing hormone hnRNA but does not affect c-fos mRNA or fos protein expression in the paraventricular nucleus of the hypothalamus. Journal of Neuroendocrinology1510751083. (doi:10.1046/j.1365-2826.2003.01100.x)

    • Search Google Scholar
    • Export Citation
  • GirottiMPaceTWWGaylordRIRubinBAHermanJPSpencerRL2006Habituation to repeated restraint stress is associated with lack of stress-induced c-fos expression in primary sensory processing areas of the rat brain. Neuroscience13810671081. (doi:10.1016/j.neuroscience.2005.12.002)

    • Search Google Scholar
    • Export Citation
  • GirottiMWeinbergMSSpencerRL2007Differential responses of hypothalamus–pituitary–adrenal axis immediate early genes to corticosterone and circadian drive. Endocrinology14825422552. (doi:10.1210/en.2006-1304)

    • Search Google Scholar
    • Export Citation
  • GrewalSSYorkRDStorkPJ1999Extracellular-signal-regulated kinase signalling in neurons. Current Opinion in Neurobiology9544553. (doi:10.1016/S0959-4388(99)00010-0)

    • Search Google Scholar
    • Export Citation
  • GustafssonJACarlstedt-DukeJPoellingerLOkretSWikströmACBrönnegårdMGillnerMDongYFuxeKCintraA1987Biochemistry, molecular biology, and physiology of the glucocorticoid receptor. Endocrine Reviews8185234. (doi:10.1210/edrv-8-2-185)

    • Search Google Scholar
    • Export Citation
  • GuzowskiJFSetlowBWagnerEKMcGaughJL2001Experience-dependent gene expression in the rat hippocampus after spatial learning: a comparison of the immediate-early genes. Arc c-fos and zif268 Journal of Neuroscience2150895098.

    • Search Google Scholar
    • Export Citation
  • HermanJP1993Regulation of adrenocorticosteroid receptor mRNA expression in the central nervous system. Cellular and Molecular Neurobiology13349372. (doi:10.1007/BF00711577)

    • Search Google Scholar
    • Export Citation
  • HermanJPCullinanWE1997Neurocircuitry of stress: central control of the hypothalamo-pituitary–adrenocortical axis. Trends in Neurosciences207884. (doi:10.1016/S0166-2236(96)10069-2)

    • Search Google Scholar
    • Export Citation
  • ImakiTKatsumataHMiyataMNaruseMImakiJMinamiS2001Expression of corticotropin-releasing hormone type 1 receptor in paraventricular nucleus after acute stress. Neuroendocrinology73293301. (doi:10.1159/000054646)

    • Search Google Scholar
    • Export Citation
  • IssaRXieSKhorasaniNSukkarMAdcockIMLeeK-YChungKF2007Corticosteroid inhibition of growth-related oncogene protein-α via mitogen-activated kinase phosphatase-1 in airway smooth muscle cells. Journal of Immunology17873667375.

    • Search Google Scholar
    • Export Citation
  • JeanneteauFDLambertWMIsmailiNBathKGLeeFSGarabedianMJChaoMV2012BDNF and glucocorticoids regulate corticotrophin-releasing hormone (CRH) homeostasis in the hypothalamus. PNAS10913051310. (doi:10.1073/pnas.1114122109)

    • Search Google Scholar
    • Export Citation
  • KasselOSanconoAKrätzschmarJKreftBStassenMCatoAC2001Glucocorticoids inhibit MAP kinase via increased expression and decreased degradation of MKP-1. EMBO Journal2071087116. (doi:10.1093/emboj/20.24.7108)

    • Search Google Scholar
    • Export Citation
  • KeyseSM2000Protein phosphatases and the regulation of mitogen-activated protein kinase signalling. Current Opinion in Cell Biology12186192. (doi:10.1016/S0955-0674(99)00075-7)

    • Search Google Scholar
    • Export Citation
  • KhanAMWattsAG2004Intravenous 2-deoxy-d-glucose injection rapidly elevates levels of the phosphorylated forms of p44/42 mitogen-activated protein kinases (extracellularly regulated kinases 1/2) in rat hypothalamic parvicellular paraventricular neurons. Endocrinology145351359. (doi:10.1210/en.2003-0539)

    • Search Google Scholar
    • Export Citation
  • KhanAMPonzioTASanchez-WattsGStanleyBGHattonGIWattsAG2007Catecholaminergic control of mitogen-activated protein kinase signaling in paraventricular neuroendocrine neurons in vivo and in vitro: a proposed role during glycemic challenges. Journal of Neuroscience2773447360. (doi:10.1523/JNEUROSCI.0873-07.2007)

    • Search Google Scholar
    • Export Citation
  • KhanAMKaminskiKLSanchez-WattsGPonzioTAKuzmiskiJBBainsJSWattsAG2011MAP kinases couple hindbrain-derived catecholamine signals to hypothalamic adrenocortical control mechanisms during glycemia-related challenges. Journal of Neuroscience311847918491. (doi:10.1523/JNEUROSCI.4785-11.2011)

    • Search Google Scholar
    • Export Citation
  • KodamaMRussellDSDumanRS2005Electroconvulsive seizures increase the expression of MAP kinase phosphatases in limbic regions of rat brain. Neuropsychopharmacology30360371. (doi:10.1038/sj.npp.1300588)

    • Search Google Scholar
    • Export Citation
  • KomatsuKJonoHLimJHImasatoAXuHKaiHYanCLiJ-D2008Glucocorticoids inhibit nontypeable Haemophilus influenzae-induced MUC5AC mucin expression via MAPK phosphatase-1-dependent inhibition of p38 MAPK. Biochemical and Biophysical Research Communications377763768. (doi:10.1016/j.bbrc.2008.10.091)

    • Search Google Scholar
    • Export Citation
  • KovácsKJSawchenkoPE1996Sequence of stress-induced alterations in indices of synaptic and transcriptional activation in parvocellular neurosecretory neurons. Journal of Neuroscience16262273.

    • Search Google Scholar
    • Export Citation
  • LoebrichSNediviE2009The function of activity-regulated genes in the nervous system. Physiological Reviews8910791103. (doi:10.1152/physrev.00013.2009)

    • Search Google Scholar
    • Export Citation
  • LuoXKissARabadan-DiehlCAguileraG1995Regulation of hypothalamic and pituitary corticotropin-releasing hormone receptor messenger ribonucleic acid by adrenalectomy and glucocorticoids. Endocrinology13638773883. (doi:10.1210/en.136.9.3877)

    • Search Google Scholar
    • Export Citation
  • MaierJVBremaSTuckermannJHerzerUKleinMStassenMMoorthyACatoACB2007Dual specificity phosphatase 1 knockout mice show enhanced susceptibility to anaphylaxis but are sensitive to glucocorticoids. Molecular Endocrinology2126632671. (doi:10.1210/me.2007-0067)

    • Search Google Scholar
    • Export Citation
  • MakinoSSchulkinJSmithMAPacákKPalkovitsMGoldPW1995Regulation of corticotropin-releasing hormone receptor messenger ribonucleic acid in the rat brain and pituitary by glucocorticoids and stress. Endocrinology13645174525. (doi:10.1210/en.136.10.4517)

    • Search Google Scholar
    • Export Citation
  • Nicoletti-CarvalhoJELellis-SantosCYamanakaTSNogueiraTCCaperutoLCLeiteARAnhêGFBordinS2010MKP-1 mediates glucocorticoid-induced ERK1/2 dephosphorylation and reduction in pancreatic β-cell proliferation in islets from early lactating mothers. American Journal of Physiology. Endocrinology and Metabolism299E1006E1015. (doi:10.1152/ajpendo.00341.2010)

    • Search Google Scholar
    • Export Citation
  • OkunoH2011Regulation and function of immediate-early genes in the brain: beyond neuronal activity markers. Neuroscience Research69175186. (doi:10.1016/j.neures.2010.12.007)

    • Search Google Scholar
    • Export Citation
  • OsterlundCSpencerR2011Corticosterone pretreatment suppresses stress-induced hypothalamic–pituitary–adrenal axis activity via multiple actions that vary with time, site of action, and de novo protein synthesis. Journal of Endocrinology208311322. (doi:10.1530/JOE-10-0413)

    • Search Google Scholar
    • Export Citation
  • OsterlundCDJarvisEChadayammuriAUnnithanRWeiserMJSpencerRL2011Tonic, but not phasic corticosterone, constrains stress activated extracellular-regulated-kinase 1/ 2 immunoreactivity within the hypothalamic paraventricular nucleus. Journal of Neuroendocrinology2312411251. (doi:10.1111/j.1365-2826.2011.02220.x)

    • Search Google Scholar
    • Export Citation
  • PaceTColeMWardGKalmanBSpencerR2001Acute exposure to a novel stressor further reduces the habituated corticosterone response to restraint in rats. Stress4319331. (doi:10.3109/10253890109014755)

    • Search Google Scholar
    • Export Citation
  • PaceTWWGaylordRTopczewskiFGirottiMRubinBSpencerRL2005Immediate-early gene induction in hippocampus and cortex as a result of novel experience is not directly related to the stressfulness of that experience. European Journal of Neuroscience2216791690. (doi:10.1111/j.1460-9568.2005.04354.x)

    • Search Google Scholar
    • Export Citation
  • PaceTWWGaylordRIJarvisEGirottiMSpencerRL2009Differential glucocorticoid effects on stress-induced gene expression in the paraventricular nucleus of the hypothalamus and ACTH secretion in the rat. Stress12400411. (doi:10.1080/10253890802530730)

    • Search Google Scholar
    • Export Citation
  • PattersonKIBrummerTO'BrienPMDalyRJ2009Dual-specificity phosphatases: critical regulators with diverse cellular targets. Biochemical Journal418475489. (doi:10.1042/BJ20082234)

    • Search Google Scholar
    • Export Citation
  • PaxinosGWatsonCREmsonPC1980AChE-stained horizontal sections of the rat brain in stereotaxic coordinates. Journal of Neuroscience Methods3129149. (doi:10.1016/0165-0270(80)90021-7)

    • Search Google Scholar
    • Export Citation
  • RadleyJJAriasCMSawchenkoPE2006Regional differentiation of the medial prefrontal cortex in regulating adaptive responses to acute emotional stress. Journal of Neuroscience261296712976. (doi:10.1523/JNEUROSCI.4297-06.2006)

    • Search Google Scholar
    • Export Citation
  • ReulJMde KloetER1985Two receptor systems for corticosterone in rat brain: microdistribution and differential occupation. Endocrinology11725052511. (doi:10.1210/endo-117-6-2505)

    • Search Google Scholar
    • Export Citation
  • SawchenkoPEBrownERChanRKEricssonALiHYRolandBLKovácsKJ1996The paraventricular nucleus of the hypothalamus and the functional neuroanatomy of visceromotor responses to stress. Progress in Brain Research107201222.

    • Search Google Scholar
    • Export Citation
  • SchulkinJGoldPWMcEwenBS1998Induction of corticotropin-releasing hormone gene expression by glucocorticoids: implication for understanding the states of fear and anxiety and allostatic load. Psychoneuroendocrinology23219243. (doi:10.1016/S0306-4530(97)00099-1)

    • Search Google Scholar
    • Export Citation
  • SgambatoVPagèsCRogardMBessonMJCabocheJ1998Extracellular signal-regulated kinase (ERK) controls immediate early gene induction on corticostriatal stimulation. Journal of Neuroscience1888148825.

    • Search Google Scholar
    • Export Citation
  • SharmaDBhaveSGreggEUhtR2013Dexamethasone induces a putative repressor complex and chromatin modifications in the CRH promoter. Molecular Endocrinology2711421152. (doi:10.1210/me.2013-1079)

    • Search Google Scholar
    • Export Citation
  • ShippLELeeJVYuC-YPufallMZhangPScottDKWangJ-C2010Transcriptional regulation of human dual specificity protein phosphatase 1 (DUSP1) gene by glucocorticoids. PLoS ONE5e13754. (doi:10.1371/journal.pone.0013754)

    • Search Google Scholar
    • Export Citation
  • ShipstonMJ1995Mechanism(s) of early glucocorticoid inhibition of adrenocorticotropin secretion from anterior pituitary corticotropes. Trends in Endocrinology and Metabolism6261266. (doi:10.1016/1043-2760(95)00149-2)

    • Search Google Scholar
    • Export Citation
  • SpencerRL1993Diurnal differences in basal and acute stress levels of type I and type II adrenal steroid receptor activation in neural and immune tissues. Endocrinology13319411950. (doi:10.1210/en.133.5.1941)

    • Search Google Scholar
    • Export Citation
  • SunHCharlesCHLauLFTonksNK1993MKP-1 (3CH134), an immediate early gene product, is a dual specificity phosphatase that dephosphorylates MAP kinase in vivo. Cell75487493. (doi:10.1016/0092-8674(93)90383-2)

    • Search Google Scholar
    • Export Citation
  • SwansonLWSimmonsDM1989Differential steroid hormone and neural influences on peptide mRNA levels in CRH cells of the paraventricular nucleus: a hybridization histochemical study in the rat. Journal of Comparative Neurology285413435. (doi:10.1002/cne.902850402)

    • Search Google Scholar
    • Export Citation
  • SweattJD2001The neuronal MAP kinase cascade: a biochemical signal integration system subserving synaptic plasticity and memory. Journal of Neurochemistry76110. (doi:10.1046/j.1471-4159.2001.00054.x)

    • Search Google Scholar
    • Export Citation
  • TchenCRMartinsJRSPaktiawalNPerelliRSaklatvalaJClarkAR2010Glucocorticoid regulation of mouse and human dual specificity phosphatase 1 (DUSP1) genes: unusual cis-acting elements and unexpected evolutionary divergence. Journal of Biological Chemistry28526422652. (doi:10.1074/jbc.M109.037309)

    • Search Google Scholar
    • Export Citation
  • TheodosiouAAshworthA2002MAP kinase phosphatases. Genome Biology3REVIEWS3009. (doi:10.1186/gb-2002-3-7-reviews3009)

  • VandevyverSDejagerLVan BogaertTKleymanALiuYTuckermannJLibertC2012Glucocorticoid receptor dimerization induces MKP1 to protect against TNF-induced inflammation. Journal of Clinical Investigation12221302140. (doi:10.1172/JCI60006)

    • Search Google Scholar
    • Export Citation
  • WaltereitRWellerM2003Signaling from cAMP/PKA to MAPK and synaptic plasticity. Molecular Neurobiology2799106. (doi:10.1385/MN:27:1:99)

    • Search Google Scholar
    • Export Citation
  • WangXNelinLDKuhlmanJRMengXWeltySELiuY2008The role of MAP kinase phosphatase-1 in the protective mechanism of dexamethasone against endotoxemia. Life Sciences83671680. (doi:10.1016/j.lfs.2008.09.003)

    • Search Google Scholar
    • Export Citation
  • WattsAG2005Glucocorticoid regulation of peptide genes in neuroendocrine CRH neurons: a complexity beyond negative feedback. Frontiers in Neuroendocrinology26109130. (doi:10.1016/j.yfrne.2005.09.001)

    • Search Google Scholar
    • Export Citation
  • WeinbergMGirottiMSpencerR2007Restraint-induced fra-2 and c-fos expression in the rat forebrain: relationship to stress duration. Neuroscience150478486. (doi:10.1016/j.neuroscience.2007.09.013)

    • Search Google Scholar
    • Export Citation
  • WeinbergMSJohnsonDCBhattAPSpencerRL2010Medial prefrontal cortex activity can disrupt the expression of stress response habituation. Neuroscience168744756. (doi:10.1016/j.neuroscience.2010.04.006)

    • Search Google Scholar
    • Export Citation
  • WeiserMJOsterlundCSpencerRL2011Inhibitory effects of corticosterone in the hypothalamic paraventricular nucleus (PVN) on stress-induced adrenocorticotrophic hormone secretion and gene expression in the PVN and anterior pituitary. Journal of Neuroendocrinology2312311240. (doi:10.1111/j.1365-2826.2011.02217.x)

    • Search Google Scholar
    • Export Citation
  • ZhouYLingE-ADheenST2007Dexamethasone suppresses monocyte chemoattractant protein-1 production via mitogen activated protein kinase phosphatase-1 dependent inhibition of Jun N-terminal kinase and p38 mitogen-activated protein kinase in activated rat microglia. Journal of Neurochemistry102667678. (doi:10.1111/j.1471-4159.2007.04535.x)

    • Search Google Scholar
    • Export Citation