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7401077 
Journal Article 
The maturation of the salmon GnRH system and its regulation by gonadal steroids in masu salmon 
Amano, M; Ikuta, K; Kitamura, S; Aida, K 
1997 
Yes 
Fish Physiology and Biochemistry
ISSN: 0920-1742
EISSN: 1573-5168 
17 
1-6 
63-70 
WOS:000071981100009 
Pituitary gonadotropin (GTH) secreting cells and brain gonadotropin-releasing hormone (GnRH) secreting neurons are known to be subjected to feedback control by gonadal steroid in teleosts. In masu salmon, Oncorhynchus masou, salmon GnRH (sGnRH) neurons in the ventral telencephalon (VT) and the preoptic area (POA) are involved in the control of GTH cells because sGnRH synthesis in these areas is activated with gonadal maturation. In this study, we attempted to clarify mechanisms of feedback control of sGnRH neurons by gonadal steroids. We examined the effects of 17 alpha-methyltestosterone (MT) on sGnRH synthesis in yearling and 2-year-old female fish (which were immature during experimentation in May), and the effects of castration on sGnRH synthesis in underyearling precocious male fish in August. sGnRH synthesis in the POA, but not in the VT, was increased by MT administration in 2-year-old females only, indicating higher sensitivity to MT in the preoptic sGnRH neurons. Castration increased sGnRH synthesis in the VT but not in the POA. These results suggest that sGnRH neurons in the VT and those in the POA are differentially regulated by gonadal steroids. 
salmon GnRH; in situ hybridization; masu salmon; castration; precocious; steroids