| In men
who have a functional etiology to their erectile
dysfunction, the treatment strategy takes a psychiatric
approach, namely, attention to partners and functional
disorders, appropriate use or nonuse of psychotropic (as
well as nonpsychotropic) drugs, managing problems of
self-esteem, and supervising appropriate lifestyle
changes.1-3 Although often effective in
cases of true functional etiology, psychiatric approaches
have proved seriously limited in the much more common
situation in which the cause of erectile dysfunction is
multifactorial. Typically, some combination of alcohol,
diabetes, smoking, hypertension, and antihypertensive or
psychotropic drugs may create or magnify partner
problems, produce performance anxiety, and cause a
detumescing downward spiral of male sexual dysfunction.1-3 Dopamine: The physiology of the male sexual response starts in the CNS. Libido, arousal, and pleasure seem to be mediated in the mesolimbic “pleasure center,” which utilizes dopamine as the pleasure neurotransmitter. Boosting dopamine may enhance sexual response, whereas blocking it may compromise sexual response.4 Thus, pro-dopaminergic agents such as bupropion, methylphenidate, and amphetamine may be good for sex, and dopamine receptor blocking antipsychotics may be bad for sex.4 |
Serotonin:
The Bad-for-Sex Neurotransmitter Serotonin seems to be a spoilsport in terms of the sexual response, possibly at 2 levels in the CNS. First, serotonin may diminish the release of pleasurable dopamine in the mesolimbic pleasure center.4 Second, serotonin, via a serotonin-2 receptor, may block the ejaculatory and orgasmic response at the level of spinal reflex centers that innervate the penis with sympathetic and parasympathetic nerves.4 Thus, agents that boost serotonin (such as serotonin selective reuptake inhibitors) can be bad for sex, whereas agents that block serotonin-2 receptors (such as nefazodone and mirtazapine) fail to produce these sexual problems.4 Prostaglandin: A Painful Alternative Smooth muscle relaxation is now known to be the key element to attaining an erection. Administration of prostaglandins can relax penile smooth muscle and elicit erections in a manner that mimics typical physiologic mechanisms.5 Thus, intracavernous injection of the prostaglandin alprostadil produces erections not only in men with organic causes of impotence, but also in men with functional causes, and even in the common situation of multifactorial causes.5 Limitations of this somewhat masochistic approach include unacceptability of self-injection, lack of spontaneity, and the possibility of too much of a good thing, namely a prolonged and painful erection called priapism. |
Yes,
There Is NO Neurotransmitter in the Penis In last month's Brainstorms, nitric oxide (NO) was shown to be a CNS neurotransmitter. But it is more. NO also functions as the neurotransmitter that relaxes smooth muscle in the penis to cause a physiologic erection during normal male sexual response by stimulating guanylyl cyclase to manufacture cGMP. It is this cGMP which then relaxes the penile smooth muscle and produces a physiologic erection.1,3,6 Once cGMP is destroyed by phosphodiesterase, the penis detumesces. This observation led to the proposal that if cGMP could somehow be enhanced, perhaps so could physiologic erections. In fact, the novel drug sildenafil (Viagra), about to be released by the FDA, works in this very manner.7-9 Anti-Phosphodiesterase Revival The strategy of phosphodiesterase inhibition has three potential advantages7-9: it allows oral administration; it leads to erections during physiologic sexual arousal (not requiring on-demand mechanics); and it boosts the most common type of problem, namely partial, intermittent erectile dysfunction of multifactorial causation.
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