Role of the lateral preoptic area and the bed nucleus of stria terminalis in the regulation of penile erection

To elucidate the role of the preoptic area (POA) in the regulation of penile erection, we examined the effects of electrical stimulation in and around the POA on penile erection in rats, which was assessed by changes in pressure in the corpus spongiosum of the penis (CSP) and electromyography (EMG) of the bulbospongiosus (BS) muscle. In unanesthetized and anesthetized rats, four types of responses were induced by stimulation in and around the POA; (1) normal type responses, which were similar to spontaneously occurring erections, characterized by slow increase in CSP pressure and sharp peaks concurrent with BS muscle bursting; (2) muscular type responses, which included sharp CSP pressure peaks (muscular component) with almost no vascular component; (3) mixed type responses, which included a sequence of high-frequency CSP peaks followed by low-frequency CSP peaks; and (4) micturition type responses, which had higher-frequency and lower-amplitude CSP peaks than other responses which were identical to those of normal micturition. In unanesthetized condition, erections were evoked by stimulation of the lateral preoptic area (LPOA), medial preoptic area (MPOA), bed nucleus of the stria terminalis (BST), paraventricular nucleus (PVN), reuniens thalamic nucleus (Re) and lateral septum (LS). Lower-intensity stimulation evoked erections from the LPOA, BST, PVN and RE, but not the MPOA. In anesthetized condition, stronger stimuli were required and effective sites were restricted to the LPOA, MPOA and BST.These findings suggest that the lateral and medial subdivisions of the preoptic area play different roles in mediating penile erection.

Research Highlight
► Penile erection was electrically evoked effectively from the LPOA, BST and PVN.
► The MPOA was less effective.