The effect of testosterone and of castration on anococcygeus muscle contractility and on plasma corticosterone levels in the rat.

The effect of testosterone and of castration on the contractility of the rat anococcygeus muscle, on plasma corticosterone concentrations, and on adrenal gland weights, was investigated. Castration was without effect on smooth muscle reactivity. However, testosterone increased muscle contractility to both NA and ACh, when given to control or castrated rats. Castration reduced both plasma corticosterone and adrenal gland weight, and this effect could be reversed by testosterone. It is concluded that changes in circulating testosterone levels cannot explain the lack of effect of adrenalectomy on muscle contractility. The possible mechanism of action of testosterone is discussed.