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

Winfried G. Rossmanith, Daniel Marks, Donald K. Clifton, Robert A. Steiner

Research output: Contribution to journalArticle

40 Citations (Scopus)

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 μg 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 ± 3 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.

Original languageEnglish (US)
Pages (from-to)185-191
Number of pages7
JournalJournal of Neuroendocrinology
Volume8
Issue number3
StatePublished - Mar 1996
Externally publishedYes

Fingerprint

Galanin
Gonadotropin-Releasing Hormone
Progesterone
Estradiol
Neurons
Messenger RNA
Complementary RNA
Gonadotropins
In Situ Hybridization
Digoxigenin
Proestrus

Keywords

  • Galanin mRNA
  • Gonadotropin-releasing hormone (GnRH) estradiol
  • Hypothalamus
  • In situ hybridization
  • Progesterone

ASJC Scopus subject areas

  • Endocrinology
  • Neuroscience(all)

Cite this

Induction of galanin mRNA in GnRH neurons by estradiol and its facilitation by progesterone. / Rossmanith, Winfried G.; Marks, Daniel; Clifton, Donald K.; Steiner, Robert A.

In: Journal of Neuroendocrinology, Vol. 8, No. 3, 03.1996, p. 185-191.

Research output: Contribution to journalArticle

Rossmanith, Winfried G. ; Marks, Daniel ; Clifton, Donald K. ; Steiner, Robert A. / Induction of galanin mRNA in GnRH neurons by estradiol and its facilitation by progesterone. In: Journal of Neuroendocrinology. 1996 ; Vol. 8, No. 3. pp. 185-191.
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T1 - Induction of galanin mRNA in GnRH neurons by estradiol and its facilitation by progesterone

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N2 - 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 μg 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 ± 3 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.

AB - 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 μg 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 ± 3 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.

KW - Galanin mRNA

KW - Gonadotropin-releasing hormone (GnRH) estradiol

KW - Hypothalamus

KW - In situ hybridization

KW - Progesterone

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