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The neuroendocrine response to sexual activity in humans is characterized by a pronounced orgasm-dependent increase of plasma levels of prolactin. In contrast to the well-known inhibitory effects of chronic hyperprolactinemia on sexual drive and function, the impact of acute prolactin alterations on human sexual physiology is unknown. Therefore, this study was designed to investigate the effects of acute manipulation of plasma prolactin on sexual behavior. Ten healthy males participated in a single-blind, placebo-controlled, balanced cross-over design. Prolactin levels were pharmacologically increased to high levels (protirelin, 50 micro g i.v.) or reduced to low physiological concentrations (cabergoline, 0.5 mg p.o.). Sexual arousal and orgasm were then induced by an erotic film and masturbation. In addition to continuous neuroendocrine and cardiovascular recordings, the quality and intensity of the acute sexual drive, arousal, orgasm and refractory period were assessed by extensive psychometric measures. Administration of cabergoline decreased prolactin levels and significantly enhanced all parameters of sexual drive (P<0.05), function (P<0.01) and positive perception of the refractory period (P<0.01). Administration of protirelin increased prolactin concentrations and produced small, but not significant reductions of sexual parameters. The sexual effects observed from cabergoline were completely abrogated by coadministration of protirelin. Although different pharmacological sites of action of prolactin-altering drugs have to be considered, these data demonstrate that acute changes in prolactin plasma levels may be one factor modulating sexual drive and function. Therefore, besides a neuroendocrine reproductive reflex, a post-orgasmic prolactin increase may represent one factor modulating central nervous system centers controlling sexual drive and behavior. These findings may offer a new pharmacological approach for the treatment of sexual disorders.

Background: Several pharmacotherapeutic approaches have confirmed the influence of neuroendocrine parameters on sexual desire, function, and fantasies in men; however, the relevance of acute neuroendocrine changes in mediating heightened sexual drive remains unknown. We recently demonstrated that plasma prolactin substantially increases following orgasm in healthy men, suggesting a feedback mechanism for peripheral prolactin in the control of acute sexual arousal. Because prolactin appears to play a regulatory role in acute sexual drive, we initiated this study to see whether sexual offenders with a high sexual drive have a different neuroendocrine response to sexual arousal. This study compares the prolactin response to orgasm of sexual offenders with high sexual drive and that of healthy subjects with average sexual drive., Methods: From a subject pool of 150 inpatients held because of sexual crimes, we recruited 10 volunteers, based on their high sexual drive according to an intensive, semistructured clinical interview. We defined sexual drive by a short refractory period and strong sexualization, or a high frequency of sexual stimulation. We analyzed the acute psychoneuroendocrine response to sexual arousal and orgasm continuously before, during, and after masturbation-induced orgasm in patients and control subjects., Results: Sexual offenders demonstrated higher sexual desire (P < 0.001) and function (P < 0.001) and a more positively perceived refractory period (P < 0.05). Both groups displayed a prolonged, significant increase in prolactin plasma levels after orgasm (P < 0.001). Sexual offenders did not differ from control subjects in neuroendocrine response to sexual arousal and orgasm., Conclusions: These data demonstrate that sexual offenders with a high sexual drive do not differ from control subjects in the postorgasmic neuroendocrine response, particularly in prolactin release. This study confirms that factors other than peripheral hormones influence deviant sexual behaviour.

In several studies we have recently demonstrated that orgasm induces prolactin secretion in healthy males and females. This suggests that prolactin may form a feedback regulator of the refractory period following orgasm. To examine this position we investigated the prolactin response of a healthy multi-orgasmic male subject. Blood was drawn continuously during masturbation-induced orgasm. The prolactin response of the case-subject was compared with that of nine healthy adult men with a normal refractory period. The case-subject showed no prolactin response to three orgasms. Data from this multi-orgasmic subject support the hypothesized role of plasma prolactin in contributing to sexual-satiation mechanisms.