Neurotransmitters and Sexual Functioning

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Sexual functioning is mediated and influenced, in a complex manner, by endocrine factors, neurotransmitters and neuropeptides.
The endocrine factors include androgens, estrogens, progesterone, prolactin, oxytocin, cortisol and pheromones. Neurotransmitters that are implicated in sexual functioning, mainly dopamine, serotonin and epinephrine, are also implicated in the pathophysiology of the major psychiatric disorders and in their pharmacological treatment.

Dopamine

Studies in humans and animals have suggested that the central dopaminergic system is involved in all components of male sexual behavior: desire, erection, orgasm and satisfaction. Dopaminergic agonists such as L-dopa, apomorphine, amantadine, bupropion and amphetamines have been reported to arouse sexual behavior while central dopaminergic blockers, like antipsychotics, suppress sexual functioning in both animals and humans.

Serotonin

Findings from animal studies suggest that 5-HT may facilitate, inhibit, or have no effect on sexual behavior, depending on which serotonin receptor subtype is involved. Studies on the effect of antidepressants on human sexual functioning suggest that activation of the 5-HT2 receptor impairs all stages of sexual response in males and females. Paroxetine, an SSRI, has been shown to be also a nitric oxide synthase inhibitor, and may diminish nitric oxide levels and function.

Epinephrine

Epinephrine inhibits erectile response in men, while blocking _1-receptors stimulates erection. By contrast, in women epinephrine facilitates vasocongestion while suppression of adrenergic activity impairs sexual arousal and orgasm.

Norepinephrine

Norepinephrine levels increase during sexual arousal in both men and women. The few studies that were done so far on this subject suggest that increasing the level of norepinephrine may facilitate erectile response in men.

Acetylcholine

Acetylcholine facilitates penile erection via the relaxation of smooth muscles of the corpus cavernosum. The role of acetylcholine in female vasocongestion is unclear.