Release of gonadotropin-releasing hormone from the Japanese quail hypothalamus in vitro

The regulation of GnRH (gonadotropin-releasing hormone) secretion in Japanese quail was studied by maintaining excised hypothalamic slices containing the median eminence region in a continuous flow superfusion system. GnRH released into the superfusate was measured by radioimmunoassay using an antibody generated against synthetic GnRH. GnRH secretion increased in a dose-response manner when hypothalamic slices from female quail were exposed to superfusion medium containing elevated potassium ion concentrations. The potassium-induced GnRH release was found to be calcium dependent. GnRH was also increased when either 1 × 10^-6 M norepinephrine, epinephrine, or 1 × 10^-5 M of the β-adrenergic agonist, isoproterenol was added to the superfusion medium. GnRH secretion from hypothalami of castrate and intact male quail was measured on Days 1, 10, and 21 of photostimulation and was elevated on Day 21. No differences were observed between the castrate and intact groups. It is concluded that GnRH is released from the quail hypothalamus in a manner analogous to mammals and that its release is subject to adrenergic stimulation.