[Central nervous control of erection]

Penile erection is caused by a change of the activity of efferent autonomic pathways to the erectile tissues and of somatic pathways to the perineal striated muscles. The sympathic outflow is mainly antierectile, the sacral parasympathic outflow is proerectile and the pudendal outflow, through contraction of the perineal striated muscles, enhances an erection already present. Spinal neurones controlling erection are activated by afferents from the genitals. It is likely that these primary afferents do not directly stimulate the spinal sympathetic, parasympathetic and somatic nuclei, but do through spinal interneurones. This spinal network is able of integrating information from periphery to elicit reflexive erections. It also receives supraspinal descending pathways from pons and hypothalamic nuclei, among the latter, the paraventricular nucleus and the medial preoptic area. These structures are likely involved to regulate penile erection in more integrated and coordinated responses occurring during sexual behavior. By receiving ascending projections from the spinal level which convoy informations from genitals, they could reinforce penile erection. Role of putative neuromediators or regulatory peptides is evoked.