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Induction of galanin mRNA in GnRH neurons by estradiol and its facilitation by progesterone

Show simple item record Steiner, Robert A. en_US Clifton, Donald K. en_US Rossmanith, Winfried G. en_US Marks, Daniel L. en_US 2008-10-17T20:40:47Z 2008-10-17T20:40:47Z 1996-03 en_US
dc.identifier.citation J Neuroendocrinol. 1996 Mar;8(3):185-91 en_US
dc.description.abstract On the day of proestrus in the rat, rising plasma levels of estradiol (E) act in concert with progesterone (P) to trigger a preovulatory release of gonadotropins. Cellular levels of galanin mRNA in GnRH neurons are increased in association with the proestrous surge of gonadotropin secretion; however, the relative contribution made by E and P to the induction of galanin mRNA expression in GnRH neurons is unknown. We investigated the role of E and P in the induction of galanin gene expression in GnRH neurons by examining the effects of different combinations of E (estradiol benzoate; 50 micrograms and P (5 mg)) on the LH surge and the concomitant induction of galanin mRNA in GnRH neurons. We sacrificed ovariectomized adult rats after 1 of 4 treatments: Group 1: vehicle control (n = 6); Group 2: P alone (n = 7) Group 3: E alone (n = 7); Group 4: combined E/P (n = 6); the animals were killed at 18.00 h at the time of the LH surge. The brains from these animals were processed by double-label in situ hybridization to allow measurement of galanin mRNA levels in GnRH neurons. GnRH neurons were identified with a digoxigenin-labeled cRNA probe for GnRH mRNA, and galanin mRNA was detected and measured simultaneously with an 35S-labeled cRNA probe coupled with computerized grain counting. Estimation of cellular levels of GnRH mRNA was accomplished with single-label in situ hybridization, an 35S-labeled GnRH cRNA probe and computerized grain counting. We observed a 3-fold induction of galanin mRNA in the GnRH neurons of animals treated with E alone compared with those treated with the vehicle alone (vehicle: 13 +/- 2 vs E: 42 +/- 4 grains/cell (g/c); P < 0.01); LH levels in the E-treated animals were elevated, albeit moderately, with respect to the vehicle controls. Compared with vehicle-treated animals, those treated with the combination of E and P showed a 5-fold induction of galanin mRNA in GnRH neurons (68 +/- 9 g/c), which was significantly (P < 0.01) greater than that observed in the animals treated with E alone; in addition, the magnitude of the LH surge was much greater (P < 0.05) in the E/P-treated group compared with the E alone group. In contrast, compared to the vehicle controls, animals treated with P alone (15 +/- 2 g/c) showed no discernable effect on galanin mRNA levels; moreover, no LH surge occurred in the P alone group. Neither the number of identified GnRH cells nor their content of GnRH mRNA differed significantly among the experimental groups (GnRH mRNA signal: vehicle controls: 153 +/- 6 vs E: 159 +/- 6 vs E/P: 153 +/- vs P: 148 +/- 8 g/c). We conclude that while E is the primary ovarian signal inducing galanin mRNA expression in GnRH neurons and the LH surge itself, P plays a facilitatory role in both of these processes. en_US
dc.language.iso en_US en_US
dc.publisher Blackwell Publishing en_US
dc.subject galanin mRNA en_US
dc.subject gonadotropin-releasing hormone (GnRH) estradiol en_US
dc.subject progesterone en_US
dc.subject in situ hybridization en_US
dc.subject hypothalamus en_US
dc.subject.mesh In Situ Hybridization en_US
dc.subject.mesh Image Processing, Computer-Assisted en_US
dc.subject.mesh Neurons, drug effects, metabolism en_US
dc.subject.mesh Progesterone, pharmacology en_US
dc.subject.mesh Luteinizing Hormone, blood en_US
dc.subject.mesh Estradiol, pharmacology en_US
dc.subject.mesh Research Support, Non-U.S. Gov't en_US
dc.subject.mesh RNA Probes en_US
dc.subject.mesh RNA, Messenger, biosynthesis en_US
dc.subject.mesh Animals en_US
dc.subject.mesh Ovariectomy en_US
dc.subject.mesh Galanin, biosynthesis en_US
dc.subject.mesh Gonadorelin, physiology en_US
dc.subject.mesh Female en_US
dc.subject.mesh Rats, Sprague-Dawley en_US
dc.subject.mesh Brain, cytology en_US
dc.subject.mesh Brain Chemistry, drug effects en_US
dc.subject.mesh Research Support, U.S. Gov't, P.H.S. en_US
dc.title Induction of galanin mRNA in GnRH neurons by estradiol and its facilitation by progesterone en_US
dc.type Article en_US

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