EFFECTS OF CASTRATION AND ANDROGEN REPLACEMENT ON THE HEMODYNAMICS OFPENILE ERECTION IN THE RAT

Previous studies from this laboratory have demonstrated that penile er ection in the rat is androgen dependent: 1 wk after castration, there was a significant decline in the magnitude of the intracavernosal pres sure (CCP) response during erection induced by stimulation of the auto nomic ganglion controlling penile blood now. The response was altered by vasoactive drugs and appeared to involve nitric oxide synthesis. Th ese earlier studies, however, did not identify the site of androgenic action or the mechanism by which the androgens act. The findings repor ted here show that even in long-term-castrated animals (up to 7 wk), t here remains a rise in CCP in response to ganglionic stimulation, demo nstrating that there is an androgen-independent as well as an androgen -dependent portion of the erectile response. Other results show a line ar relationship between systemic blood pressure and CCP during erectio n, although in castrated animals without androgen replacement, the CCP responds less to changes in the systemic pressure than in intact or t estosterone-treated animals. This finding could signify a reduced bloo d inflow and/or an increased blood outflow during erection in the cast rated rats. Further studies partially explained the lower erectile pre ssure by demonstrating that the rate of outflow from the cavernosal sp aces was greater in castrated rats than in animals with normal androge n levels. Taken together, these findings show that androgens act to ma intain both the inflow and the outflow of blood from the cavernous spa ces during erection.