A dual physiological character for sexual function: the role of serotonergic receptors.

Anatomically, sexual reflexes are mixed (somatic-autonomic) circuits, represented by emission (sympathetic centre and somatic afferents), expulsion (parasympathetic centre and somatic efferents) and erection (parasympathetic centre and somatic afferents). Physiologically, ejaculation has a dual autonomic mediation, consisting of two distinct and opposite autonomic centres (emission and expulsion), both with a positive contribution to the respective function. Experimentally, serotonin (5HT) has two distinct, opposite and positive effects on sexual function, with 5HT-(1A) agonists decreasing intravaginal ejaculatory latency and erection, and 5HT-(2C) agonists increasing both erection and ejaculatory latency. In this review I assume that 5HT modulates sexual reflexes, establishing a functional connection between the involved somatic and autonomic structures. The 5HT-(1A) receptors are assumed to make the connection between somatic pathways and sympathetic centres while the 5HT-(2C) receptors could establish the connection between somatic pathways and parasympathetic centres. Further studies will develop the cerebral sexual duality, explaining the implication of psychological factors in sexual function and the role of sexuality in psychosocial behaviour.