Serotonin and the neurobiology of the ejaculatory threshold

Disorders of the ejaculatory threshold, such as lifelong premature ejaculation, are fairly common in humans and can have a great impact on the quality of life.Research in humans and rats have indicated that increased serotonin levels in the central nervous system elevate the ejaculatory threshold, probably via 5-HT1B and 5-HT2C receptors, whereas depletion of serotonin decreases the ejaculatory threshold. 5-HT1A receptor activation strongly lowers the ejaculatory threshold, probably mediated by both the reduction of serotonin levels via presynaptic 5-HT1A receptors and yet unknown effects of postsynaptic 5-HT1A receptors.The present review attempts to integrate psychopharmacological data on serotonergic control over ejaculation with the knowledge of the neuroanatomical substrate of ejaculation, indicating the importance of the lumbosacral spinal cord, the nucleus paragigantocellularis, the lateral hypothalamic area and several other supraspinal areas. In addition, the gaps in our understanding of the role of serotonin in the ejaculatory threshold are discussed. Filling in those gaps might help to design specific drugs that alter the ejaculatory threshold, thereby alleviating ejaculatory disorders.