A steroidal pheromone and spawning stimuli act via different neuroendocrine mechanisms to increase gonadotropin and milt volume in male goldfish Carassius auratus.
In goldfish (Carassius auratus), pheromonal 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) and spawning stimuli (interaction with a sexually active female releasing prostaglandin pheromone) both increase gonadotropin-II (GtH-II) and milt volume. In the goldfish pituitary, GtH-II release is stimulated by gonadotropin-releasing hormone (GnRH) and inhibited by dopamine (DA). In this study, we investigated the possibility that 17,20beta-P and spawning stimuli act via separate neuroendocrine mechanisms by determining whether their effects on GtH-II could be selectively disrupted by injection of DA type-2 receptor (D-2) agonists (bromocryptine and LY171555) or a goldfish GnRH antagonist, [Ac-Delta3-Pro1, 4FD-Phe2, d-Trp3,6]-mGnRH (analog E). D-2 agonists blocked 17,20beta-P-induced increases in GtH-II and milt volume but did not affect spawning-induced responses. GnRH antagonist blocked 17,20beta-P-induced increases in GtH-II and milt volume, and spawning-induced GtH-II increase, but did not affect spawning-induced increase in milt volume. These results suggest that (1) pheromonal 17,20beta-P and spawning stimuli increase GtH-II increase via distinct neuroendocrine mechanisms, (2) the effect of pheromonal 17,20beta-P on increasing milt volume is GtH-II-dependent, and (3) the effect of spawning stimuli on increasing milt volume is GtH-II-independent.
Zheng
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Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
Stacey
N E
NE
D000818:Animals; D001971:Bromocriptine / Q000008:administration & dosage / Q000494:pharmacology*; D018491:Dopamine Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006054:Goldfish; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D006065:Gonadotropins, Pituitary / Q000097:blood* / Q000276:immunology; D006908:Hydroxyprogesterones / Q000008:administration & dosage / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D008297:Male; D019257:Quinpirole / Q000008:administration & dosage / Q000494:pharmacology*; D011863:Radioimmunoassay; D012661:Semen / Q000187:drug effects* / Q000502:physiology
D018491:Dopamine Agonists; D006065:Gonadotropins, Pituitary; D006908:Hydroxyprogesterones; C021012:17 alpha,20 beta-dihydroxypregn-4-en-3-one; D019257:Quinpirole; D007987:Gonadotropin-Releasing Hormone; D001971:Bromocriptine; C036959:LHRH, Ac-dehydro-Pro(1)-4-F-Phe(2)-Trp(3,6)-