Impaired sexual response after lesions of the paraventricular nucleus of the hypothalamus in male rats.

N-methyl-D-aspartic acid (NMDA) or radiofrequency (RF) lesions were made in the paraventricular nucleus of the hypothalamus (PVH) of male rats. The rats were tested for copulation, noncontact erection (NCE) evoked by remote cues from estrous females, and (after RF lesions) reflexive erection. NMDA, which destroyed parvocellular but spared magnocellular neurons, caused no deficits in copulation but caused longer NCE latencies and fewer NCEs. Rats with RF lesions had parvo- and magnocellular neuron damage; these males copulated to ejaculation, but they had lower intromission ratios and longer ejaculatory latencies. RF-lesioned rats also had longer NCE latencies, and a smaller proportion of males displayed reflexive erection. Results indicate that the PVH participates in mediating erectile function in copula and ex copula, and that the parvo- and magnocellular PVH neurons may have different roles in mediating erection.