Neurohypophysial Hormones Associated with Osmotic Challenges in the Brain and Pituitary of the Euryhaline Black Porgy, .

Our study showed differential expression of the ()/ () in the brain and pituitary gland of the euryhaline black porgy () during osmotic stress. A decrease in serum osmolality and increased cortisol levels were observed after acute transfer from seawater (SW) to freshwater (FW). The increased expressions of , (: ), and (: transcripts on day 1 and and transcripts on days 7 and 30 were found in the brains and pituitary glands of FW fish. Increased levels of mRNA in the diencephalon and mRNA in the pituitary together with serum cortisol on day 1 of FW exposure indicated activation of the hypothalamic-pituitary-interrenal (HPI) axis. The expression levels of and after FW transfer were increased in the pituitary on days 7 and 30. Furthermore, hybridization demonstrated spatially differential expression of and transcripts in nucleus preopticus parvocellularis of pars gigantocellularis (PMgc), magnocellularis (PMmc), and parvocellularis (PMpc) of the preoptic area (POA). Positive signals for and were highly abundant in PMpc after FW exposure. The data suggest involvement of neurohypophysial hormones in the brain (telencephalon and diencephalon) and pituitary for osmotic stress.