Corticosterone-induced gonadosuppression in photostimulated tree sparrows.

To explore the possibility that adrenal hormones play a role in the natural termination of testicular function in chronically photo-stimulated tree sparrows, corticosterone, the principal adrenal steroid of birds, was implanted intracerebrally in photoresponsive tree sparrows 3 weeks after they were transferred to a gonadostimulatory photoregime. Three weeks later, plasmas were assayed for immunoreactive luteinizing hormone (LH), testes were weighed, and implantation sites were determined. When implanted in a region of the basal hypothalamus known to be androgen sensitive, corticosterone reduced the concentration of plasma LH and blocked testicular growth. Control implants in the optic chiasma or tracts were not gonadoinhibitory. These results confirm the potential for inhibition of gonadotropin secretion by an effect of corticosterone on the hypothalamohypophyseal axis, but the physiological significance and mechanism of corticosterone's antigonadotropic effect remain to be established.