Effect of serotonin on the basal and gonadotrophin-releasing hormone-induced release of luteinizing hormone from rat pituitary glands in vitro.
The effect of serotonin (5-HT) on the basal and gonadotrophin-releasing hormone (GnRH)-stimulated release of luteinizing hormone (LH) was studied in rat adenohypophysis in vitro. Anterior pituitary glands from ovariectomized rats were incubated for 1h in the presence of different doses of 5-HT (0.01 to 3 mumol/l). Serotonin added to the culture medium slightly dimished the basal release of LH and markedly inhibited the release of LH induced by GnRH. Responsiveness to GnRH (3 nmol/l) was significantly reduced, in a dose-dependent manner, by the simultaneous treatment of glands with 5-HT. Maximal inhibition to 65% of the response obtained with GnRH alone, was attained with 1 mumol/l 5-HT. The EC50 value was estimated to be about 1.9 X 10(-7) M. The inhibitory effect of 5-HT was evident within 30 min of incubation. Furthermore, 5-HT appear to exert a short-lasting action, since the rate of basal and GnRH-induced release of LH was reduced during the first hour of incubation, but after 2h the suppressive effects of 5-HT were no longer apparent. Methysergide, a serotonin receptor blocking agent, partially antagonized the inhibitory effect of 5-HT on LH release, either basal or GnRH-stimulated. This suggests that a receptor-mediated component may be involved in the mechanism of 5-HT action. The present results indicate that 5-HT can affect the release of LH by acting directly at the pituitary gland level.
Apfelbaum
M E
ME
Instituto de Investigación Médica Mercedes y Martín Ferreyra, Córdoba, Argentina.
D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism*; D008784:Methysergide / Q000494:pharmacology; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*
D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D008784:Methysergide