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The major purpose of this study was to characterize the open-loop frequency of pulsatile GnRH release in the female rhesus monkey at an age (15-20 months) when the prepubertal restraint on the hypothalamic-pituitary axis is maximally imposed. Additionally, evidence for pulsatile GnRH release in agonadal males of comparable age was also sought. Episodic LH secretion from the pituitary was used as an indirect index of GnRH discharges. In order to maximize the sensitivity of this in situ bioassay, the responsiveness of the pituitary gonadotrophs was usually first heightened by an i.v. intermittent infusion of the synthetic peptide. Monkeys (five females, three males) were castrated between 9 and 14 months of age, implanted with indwelling venous catheters, fitted with nylon jackets and housed in specialized cages that permitted remote access to the venous circulation with minimal restraint and without interruption of the light-darkness cycle. In females, LH secretion was generally assessed at 20-day intervals during alternate nighttime (1900-0200 h) and daytime (0700-1400 h) windows. In males, LH was assessed less frequently and only at night. The mean frequency of pulsatile LH release in agonadal prepubertal females was 4 pulses/7 h during the night and 2 pulses/7 h during the day. These findings indicate that, prior to puberty in the female monkey, the GnRH pulse generator operates at a relatively slow frequency and is subjected to diurnal modulation. In males, evidence for robust pulsatile GnRH release was not observed. The striking difference in activity of the GnRH pulse generator in agonadal prepubertal male and female monkeys reinforces the view that the ontogeny of the hypothalamic drive to the pituitary-gonadal axis in higher primates, including man, is sexually differentiated.
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directly on the pituitary to inhibit gonadotropin release. In addition, GnIH-containing fibers were observed in extremely close proximity to gonadotropin-releasing hormone (GnRH) neurons in the preoptic area in birds ( Bentley et al. 2003 , Ukena et al
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Department of Biological Sciences, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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Department of Biological Sciences, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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the multifactorial control of somatotropes is gonadotropin-releasing hormone (GnRH), which directly stimulates GH secretion and mRNA expression both in vivo and in vitro ( Canosa et al . 2007 , Chang & Wong 2009 , Chang et al . 2012 ). Multiple
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
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Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
Division of Seasonal Biology, National Institute for Basic Biology, Okazaki, Japan
Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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hormone (GnRH) is secreted from the hypothalamus and stimulates the release of gonadotropins, such as luteinizing hormone and follicle-stimulating hormone, from the anterior pituitary gland. These hormones act on the testis and ovary to facilitate gonadal
Endocrinology, SBMS, Faculty of Medicine, The University of Queensland, St Lucia, Qld, Australia
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disturbances in reproductive and metabolic hormones. In this narrative review, an overview of the available evidence delineating various hormonal factors in women with PCOS was given. The contributing hormones include gonadotropin-releasing hormone (GnRH
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Introduction The hypothalamic–pituitary–gonadal axis is regulated by the facilitative effect of gonadotropin-releasing hormone (GnRH) in the hypothalamus of mammals and other vertebrates. In recent years, a novel avian hypothalamic neuropeptide
School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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neurohypophysical hormones ( Sawchenko et al. 1983 , Chaouloff 2000 , Kang et al. 2004 ). These findings indicate that serotonin may function as a mediator of hormone secretion. Gonadotropin-releasing hormone (GnRH) release is essential for the
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. Fernandez-Fernandez R , Aguilar E, Tena-Sempere M & Pinilla L 2005 Effects of polypeptide YY 3–36 upon luteinizing hormone-releasing hormone and gonadotropin secretion in prepubertal rats: in vivo and in vitro studies. Endocrinology 146 1403
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–pituitary–gonadal (HPG) axis in mammals. GnRH is produced by the neurosecretory cells of the hypothalamic preoptic area (POA) and is released in the median eminence (ME), where it regulates the synthesis and release of gonadotropins, follicle-stimulating hormone (FSH
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mechanism underlying LH suppression, LPS acutely suppressed the coordinated release of both gonadotropin-releasing hormone (GnRH) and LH pulses in ovariectomized (OVX) sheep, suggesting central inhibition of the GnRH pulse generator ( Battaglia et al. 1998
