Effect of castration and testosterone on norepinephrine storage and on the release of [ 3H]norepinephrine from rat vas deferens

Abstract

Norepinephrine and dopamine-β-hydroxylase, used as noradrenergic vesicle markers, were found to be decreased in the rat vas deferens 10 days after castration. Five days of testosterone administration to castrated animals increased the enzyme activity over that of controls but did not modify norepinephrine content. In tissue fractions obtained by differential centrifugation, the highest activities of the noradrenergic markers appeared in the vesicular fraction of controls and in the soluble fraction of castrated animals. Testosterone reversed the effect of castration: it increased dopamine-β-hydroxylase activity in the vesicular and soluble fractions, while norepinephrine increased only in the vesicular fraction. Results obtained after continuous sucrose gradient centrifugation of vesicular fractions suggested that these changes principally affected the number of light noradrenergic vesicles while testosterone increased the number of vesicles reduced by castration. Hormonal manipulations also modified some functional properties of nerve endings: norepinephrine depletion after transmural stimulation in the presence of tetraethylammonium, as well as the release of the neurotransmitter, were decreased after castration. These effects were reversed by testosterone. The results suggest a modulatory effect of testosterone on the norepinephrine storage system and on the functional properties of the adrenergic innervation of vas deferens.