GABA stimulation of gonadotropin-II release in goldfish: involvement of GABAA receptors, dopamine, and sex steroids
In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Jg. 265 (1993-08-01), S. R348- (8S.)
Online
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Zugriff:
The involvement of gamma-aminobutyric acid (GABA) in regulation of pituitary gonadotropin-II (GTH-II) release was studied in the goldfish. Intraperitoneal injection of GABA (300 micrograms/g) stimulated an increase in serum GTH-II levels at 30 min postinjection. The GABAA receptor agonist muscimol (0.1-10 micrograms/g) stimulated GTH-II in a dose-dependent manner. Baclofen, a GABAB receptor agonist, had a small but significant stimulatory effect at 1 and 10 micrograms/g; the amount of GTH-II released in response to baclofen was significantly less (P < 0.05) than that released by muscimol. Pretreatment of goldfish with bicuculline, a GABAA receptor antagonist, but not saclofen, a GABAB receptor antagonist, blocked the stimulatory effect of GABA on serum GTH-II. Elevation of brain and pituitary GABA levels with the GABA transaminase inhibitor, gamma-vinyl-GABA (GVG), decreased hypothalamic and pituitary dopamine (DA) turnover rates, indicating that GABA may stimulate GTH-II release in the goldfish by decreasing dopaminergic inhibition of GTH-II release. The release of GTH-II stimulated by muscimol and GVG was potentiated by pharmacological agents that decrease inhibitory dopaminergic tone, indicating that DA may also inhibit GABA-stimulated GTH-II release. Based on the linear 24-h accumulation of GABA in brain and pituitary after GVG injection, implantation of testosterone, estradiol, or progesterone, previously shown to regulate the serum GTH-II release response to gonadotropin-releasing hormone and GABA, was also found to modulate GABA synthesis in the brain and pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)
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GABA stimulation of gonadotropin-II release in goldfish: involvement of GABAA receptors, dopamine, and sex steroids
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Autor/in / Beteiligte Person: | Peter, R.E. ; Trudeau, Vance L. ; Sloley, B.D. |
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Zeitschrift: | American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Jg. 265 (1993-08-01), S. R348- (8S.) |
Veröffentlichung: | American Physiological Society, 1993 |
Medientyp: | unknown |
ISSN: | 1522-1490 (print) ; 0363-6119 (print) |
DOI: | 10.1152/ajpregu.1993.265.2.r348 |
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