Neurosteroid Biosynthesis in the Brain and Pituitary Gland of Salmonid Fishes
Fish Migration and Passage: Physiology and Behavior
Cech JJ Jr.;Swanson C;Young PC;MacKinlay DD;
American FIsheries Society, Physiology Section
The present study was conducted to investigate the relations between neurosteroid biosynthesis and their possible roles on migratory mechanisms of salmonid fishes, using sockeye salmon (Oncorhynchus nerka). First, the ability of brain to produce sex steroid hormones was examined with exogenous steroid substrates during smoltification. It was demonstrated that the brain had the ability to produce sex steroid hormones during smoltification, and the ability tended to be higher in the anterior brain than in the posterior brain. Secondly, the ability of salmon brain and pituitary to synthesize and metabolize cholesterol was examined by in vitro thin-layer chromatography method during sexual maturation. It was revealed that pregnenolone was identified as one of cholesterol metabolites in the brain and pituitary gland. These results suggest that neurosteroids are produced in the brain and pituitary gland of sockeye salmon, and might be involved in smoltification and sexual maturation of salmonid fishes.