Are the effects of androgens on male sexuality noradrenergically mediated? Some consideration of the human.

The effects of androgens on the sexuality of male rodents is likely to be mediated, at least in part, by central noradrenergic (NA) mechanisms. Davidson's group has shown this by restoring behaviour in castrated males with alpha-2 adrenoceptor antagonists. As yet, there are no comparable studies of drug administration to hypogonadal men, but relevant evidence from recent studies in eugonadal men is considered. The evidence is consistent with a role for NA mediation in human sexual arousal, but suggests that more than one NA mediated system exist, involving both central arousal and inhibition of peripheral responses such as erection. The study of spontaneous erections during REM sleep is of particular interest, as REM is accompanied by virtual cessation of peripheral sympathetic activity in relevant parts of the body. "Psychogenic" erectile dysfunction may involve a high level of central alpha-2 inhibitory tone which reduces the capacity for central arousal. On the other hand, there may be an age related loss of responsiveness to the central arousing effects of NA, suggesting that the aetiology of psychogenic erectile dysfunction may vary with age. NA mechanisms may well be involved in the mediation of androgenic effects in humans, but no simple relationship between NA and sexual response should be expected.