Stimulatory effects of serotonin on maturational gonadotropin release in the Atlantic croaker, Micropogonias undulatus.
The effects of serotonin (5-HT) injection alone, and in combination with des Gly10 [D-Trp6]-luteinizing hormone-releasing hormone ethylamide (LHRHa), on plasma maturational gonadotropin (GtH) levels in the Atlantic croaker, Micropogonias undulatus, were examined. An injection of 5-HT (20 micrograms/g body wt) alone did not significantly elevate GtH levels, whereas simulatneous administration of LHRHa (20 ng/g body wt) and 5-HT elicited a greater elevation of plasma GtH levels than that induced by LHRHa alone. Pretreatment of 1-year-old fish with fluoxetine (10 micrograms/g), a 5-HT reuptake inhibitor, only slightly augmented the effect of 5-HT on GtH levels, whereas pretreatment with ketanserin (10 micrograms/g), a 5-HT receptor antagonist, completely inhibited the potentiating effect of 5-HT on the GtH response to LHRHa. Administration of LHRHa (20 ng/g) or 5-HT (20 micrograms/g) significantly elevated GtH levels in the 2- and 3-year-old croaker, but the combined treatment failed to increase GtH levels above those induced by LHRHa alone. However, with a lower dose of LHRHa (5 ng/g), the combination produced an additive effect. Serotonin (20 micrograms/ml media) alone, and in combination with LHRHa (10 ng/ml media), significantly stimulated GtH release from the pituitaries of gonadally mature 2- and 3-year-old female croaker during an 18-hr incubation in vitro, but not from pituitaries of gonadally regressed fish. The combined treatment of LHRHa with 5-HT also significantly stimulated in vitro GtH release during 6- and 12-hr pituitary incubations, whereas these treatments alone were ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)
Khan
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IA
University of Texas, Austin, Marine Science Institute, Port Aransas 78373.
Thomas
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D000375:Aging / Q000378:metabolism; D000818:Animals; D005260:Female; D005473:Fluoxetine / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006062:Gonadotropins / Q000378:metabolism*; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D010473:Perciformes / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D012727:Sex Characteristics
D006062:Gonadotropins; D005473:Fluoxetine; D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D007650:Ketanserin