Lesions of the periaqueductal gray block the medial preoptic area-induced activation of the urethrogenital reflex in male rats.

The medial preoptic area (MPOA) is important for male sexual behavior, including erections and ejaculation. Stimulation of the MPOA evokes urethrogenital reflex-like responses. However, the descending pathways mediating this response are unknown. We examined the effect of bilateral lesions of the periaqueductal gray (PAG) on the MPOA-induced response. Electrical stimulation of the MPOA was used to induce rhythmic motor patterns of the bulbospongiosus muscle, discrete regions of the PAG were lesioned and the response to MPOA stimulation re-examined. These studies demonstrate that the descending pathway mediating the MPOA-induced activation of the urethrogenital reflex-like responses travel through and may relay in the PAG.