Activation of accessory olfactory bulb neurons during copulatory behavior after deprivation of vomeronasal inputs in male rats.

We examined whether the vomeronasal organ (VNO) is the sole receptor for pheromonal cues for male sexual behavior. Males carrying surgical removal of the VNO (VNOx) mated with stimulus females as sham-operated males, with a comparable number of mounts but a prolonged latency for ejaculation. In sham-operated males, mating increased cFos immunoreactivity in the granule and mitral cell layers of the accessory olfactory bulb and in the medial amygdala. VNOx diminished baseline as well as mating-induced cFos in the granule cell layer and in the medial amygdala; VNOx had no effect on either basal or induced cFos immunoreactivity in the mitral cell layer. Thus, during mating encounter, cFos expression in the mitral cell layer did not depend on VNO inputs. The medial amygdala may be modulated by impulses other than of mitral cell origin.