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

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Abstract
Testosterone administration to orchidectomized rats brought about a significant, 55% decrease ofβ-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 pinealβ-adrenoceptor binding. The depressive effects of testosterone inβ-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 pinealβ-adrenoceptor density caused by testosterone. Hormone effects did not depend on a direct effect of the hormone onβ-adrenoceptor sites because testosterone did not compete with [3H]-DHA for the binding sites,in vitro. These results suggest that testosterone depresses pinealβ-adrenergic sites by acting mainly on post-synaptic sites.

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