Testosterone decreases beta-adrenoceptor sites in rat pineal gland and brain

Testosterone administration to orchidectomized rats brought about a significant, 55% decrease of beta-adrenoceptor sites in the pineal gland, assessed from the specific binding of radioactive dihydroalprenolol (DHA). The changes in density of binding sites were not accompanied by significant modifications of the Kd. FSH or LH treatment of acutely castrated animals did not affect pineal beta-adrenoceptor binding. The depressive effects of testosterone in beta-adrenergic receptors were also observed in crude membrane fractions of medial basal hypothalamus and cerebral cortex. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy did not abolish the changes in pineal beta-adrenoceptor density caused by testosterone. Hormone effects did not depend on a direct effect of the hormone on beta-adrenoceptor sites because testosterone did not compete with [3H]-DHA for the binding sites, in vitro. These results suggest that testosterone depresses pineal beta-adrenergic sites by acting mainly on postsynaptic sites.