Lactation is a physiological condition known to upregulate the expression of the hypothalamic neurohormones, oxytocin and vasopressin, in the rat supraoptic and paraventricular nuclei. Other neuropeptides such as galanin are co-localized in the same magnocellular neurones and their expression has been demonstrated to be regulated by different experimental and physiological conditions. In the present study, we investigated the possible changes in galanin expression during lactation, using in situ hybridization and immunohistochemistry separately or in combination. Galanin messenger RNA concentrations decreased on day 3 of lactation in both the supraoptic and paraventricular nuclei and remained low on day 7 of lactation, but no differences were observed between control and 14-day lactating rats. In parallel, immunopositive cell bodies were almost undetectable on day 7 of lactation and immunoreactivity remained weak after 14 days of lactation, whereas galanin immunoreactive profiles in the supraoptic nucleus were more numerous than in the control group. Moreover, the subcellular distribution of immunostaining changed on day 14 of lactation. Galanin immunoreactivity was confined around the nucleus in the control females, but it became weaker and more homogenously distributed throughout the cytoplasm in the lactating rats. Electron microscopy using a pre-embedding technique confirmed that galanin immunoreactivity was no longer restricted to the Golgi complex, but was apparent throughout in the cytoplasm. Multiple labellings showed galanin and galanin messenger RNA to be co-localized with oxytocin messenger RNA in neurones of the dorsomedial part of the supraoptic nucleus during lactation. Some of those doubly labelled cells also expressed vasopressin messenger RNA in the same conditions as revealed by a triple-labelling procedure. As these co-localizations have not been observed in female control rats, lactation provided an example of a physiological condition inducing oxytocin and galanin co-synthesis in a subpopulation of magnocellular neurones. In conclusion, we have demonstrated plasticity of galanin expression during lactation in the hypothalamic magnocellular neurones. This plasticity could be caused by changes in galanin expression or in galanin processing in magnocellular neurones.
M Landry, D Roche, E Angelova and A Calas
D. Martel, M. N. Monier, D. Roche, V. J. De Feo and A. Psychoyos
The main objective of the present study was to analyse the hormonal dependence of the metrial gland formed in pseudopregnant animals following massive decidualization. On day 13 of pseudopregnancy (when the metrial gland reaches its maximal development) animals were ovariectomized and given s.c. implants of oestradiol and/or progesterone. A new implant technique for oestradiol delivery is described which provides circulating concentrations of oestradiol in the physiological range.
In addition, we extended our previous work concerning oestradiol receptor and progesterone receptor concentrations in the metrial gland of pseudopregnant rats. The low oestradiol receptor concentration which we previously reported up to day 17 was maintained until the end of pseudopregnancy (day 21–1·5 fmol/μg DNA), whereas the progesterone receptor concentration remained raised (≃3·5 fmol/μg DNA) from day 13 to day 19 and then decreased on day 21.
The correlation of metrial gland weight and kinetics of the tissue oestradiol and progesterone receptors contents with the circulating oestradiol and progesterone concentrations lead to the following conclusions. First, the maintenance of the metrial gland is strictly progesterone-dependent. It is unlike the deciduoma which regresses spontaneously, even in the presence of progesterone. Secondly, the production of oestradiol receptor, but not of progesterone receptor, appears to be repressed in the metrial gland under the influence of progesterone. Thus, the tissue retains its ability to respond to progesterone because of a high concentration of progesterone receptor. It is difficult to attribute this high tissue progesterone receptor concentration to oestradiol stimulation since, even at low levels, oestradiol induces tissue regression. We suggest that the high progesterone receptor concentration could be due to constitutive (basal) progesterone receptor production.
Journal of Endocrinology (1989) 120, 465–472
D. Martel, R. Frydman, M. Glissant, C. Maggioni, D. Roche and A. Psychoyos
The ultrastructure of the luminal surface epithelium was compared in endometrial samples taken from 23 normally cycling women and from 22 patients submitted to ovarian stimulation with clomiphene citrate (100 mg/day for 5 days), human menopausal gonadotrophin (hMG) and human chorionic gonadotrophin (hCG). On day 2 after ovulation, only four out of nine specimens taken from the women in the hormone-treated group were identical to those of normally cycling women. On day 6 after ovulation, only two out of the 13 biopsy specimens from the treated group were the same as those from normally cycling women at that stage. Apical protrusions (pinopodes), typical for this period of the cycle, were missing in 11 of the 13 endometrial samples from the treated group.
These observations suggest that the hormonal treatment applied to induce ovulation (clomiphene citrate, hMG and hCG) can modify the normal development of the prenidatory endometrium, and may thus have a negative effect on the rate of egg implantation.
J. Endocr. (1987) 114, 319–324