Endocrinology, Vol 132, 1836-1844, Copyright © 1993 by Endocrine Society

ARTICLES

Regulation of galanin gene expression in gonadotropin-releasing hormone neurons during the estrous cycle of the rat

DL Marks, MS Smith, M Vrontakis, DK Clifton and RA Steiner
Department of Physiology and Biophysics, University of Washington, Seattle 98195.

Galanin is colocalized with GnRH in neurons of the hypothalamus and basal forebrain of female rats, and this neuropeptide may play a role in the generation of the midcycle surge of gonadotropin secretion. We tested the hypothesis that galanin gene expression in GnRH cells increases during proestrus. To accomplish this, we killed groups of adult female rats at 1200 and 1800 h on the day of proestrus as well as at 1800 h on the day of estrus and used double labeling in situ hybridization and image analysis to estimate and compare the levels of galanin mRNA in cells coexpressing GnRH mRNA. GnRH mRNA was detected with an antisense cRNA probe labeled with the hapten digoxigenin, while the galanin cRNA probe was labeled with 35S and detected by autoradiography. There was no significant difference in the total number of GnRH cells identified in each animal in any of the different groups in any experiment. The relative number of silver grains over these cells, reflecting galanin mRNA content in GnRH neurons (identified by their purple color), was counted with a computerized image analysis system. In an initial experiment, we observed a 2-fold (P < 0.03) higher galanin mRNA signal level in the animals killed at 1800 h than in those killed at 1200 h on the day of proestrus. Animals killed at 1800 h on the day of estrus had galanin mRNA signal levels that were not statistically different from those in the proestrous 1800 h group, indicating that the increase in galanin mRNA at proestrus is maintained for at least 24 h. Galanin mRNA levels in GnRH neurons returned to basal levels equivalent to those in the proestrous 1200 h group by 1000 h on diestrous day 1. In conjunction with the studies of galanin gene expression in GnRH neurons, we compared the relative cellular contents of GnRH mRNA among the same groups. Here, we used single labeling isotopic in situ hybridization for GnRH mRNA and computerized image analysis to count the resulting silver grains. We could detect no difference in GnRH mRNA signal levels (proestrus, 1200 h vs. proestrus, 1800 h vs. estrus, 1800 h). In a final experiment, we investigated the possible role of estrogen in the induction of galanin mRNA expression at proestrus by comparing relative galanin mRNA contents in GnRH neurons among groups of ovariectomized, intact (diestrous day 1), and ovariectomized 17 beta-estradiol-replaced female rats.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				I. Merchenthaler, G. E. Hoffman, and M. V. Lane Estrogen and Estrogen Receptor-{beta} (ER{beta})-Selective Ligands Induce Galanin Expression within Gonadotropin Hormone-Releasing Hormone-Immunoreactive Neurons in the Female Rat Brain Endocrinology, June 1, 2005; 146(6): 2760 - 2765. [Abstract] [Full Text] [PDF]

				C. L. Splett, J. R. Scheffen, J. A. Desotelle, V. Plamann, and A. C. Bauer-Dantoin Galanin Enhancement of Gonadotropin-Releasing Hormone-Stimulated Luteinizing Hormone Secretion in Female Rats Is Estrogen Dependent Endocrinology, February 1, 2003; 144(2): 484 - 490. [Abstract] [Full Text] [PDF]

				B. Kleine, S. Wolfahrt, M. Lotsch, T. Gantner, and W. G. Rossmanith Expression of galanin in human placenta Mol. Hum. Reprod., April 1, 2001; 7(4): 379 - 385. [Abstract] [Full Text] [PDF]

				B. S. Rubin Hypothalamic Alterations and Reproductive Aging in Female Rats: Evidence of Altered Luteinizing Hormone-Releasing Hormone Neuronal Function Biol Reprod, April 1, 2000; 63(4): 968 - 976. [Abstract] [Full Text]

				J. A. Maurer and S. Wray Luteinizing Hormone-Releasing Hormone Quantified in Tissues and Slice Explant Cultures of Postnatal Rat Hypothalami Endocrinology, February 1, 1999; 140(2): 791 - 799. [Abstract] [Full Text]

				A. E. Herbison Multimodal Influence of Estrogen upon Gonadotropin-Releasing Hormone Neurons Endocr. Rev., June 1, 1998; 19(3): 302 - 330. [Abstract] [Full Text]

				S. F. Leibowitz, A. Akabayashi, J. T. Alexander, and J. Wang Gonadal Steroids and Hypothalamic Galanin and Neuropeptide Y: Role in Eating Behavior and Body Weight Control in Female Rats Endocrinology, April 1, 1998; 139(4): 1771 - 1780. [Abstract] [Full Text] [PDF]

				E. S. Shen, E. H. Meade, M. C. Perez, D. C. Deecher, A. Negro-Vilar, and F. J. Lopez Expression of Functional Estrogen Receptors and Galanin Messenger Ribonucleic Acid in Immortalized Luteinizing Hormone-Releasing Hormone Neurons: Estrogenic Control of Galanin Gene Expression Endocrinology, March 1, 1998; 139(3): 939 - 948. [Abstract] [Full Text] [PDF]

				P. D. Finn, R. A. Steiner, and D. K. Clifton Temporal Patterns of Gonadotropin-Releasing Hormone (GnRH), c-fos, and Galanin Gene Expression in GnRH Neurons Relative to the Luteinizing Hormone Surge in the Rat J. Neurosci., January 15, 1998; 18(2): 713 - 719. [Abstract] [Full Text] [PDF]