EVIDENCE OF A DIRECT PROJECTION OF THE VOMERONASAL ORGAN TO THE MEDIAL PREOPTIC NUCLEUS AND HYPOTHALAMUS

In rodents the vomeronasal system plays an important role in modulatin g the hypothalamic control of gonadotropin secretion. It is accepted t hat the anatomical pathways by which the vomeronasal organ influences the neuroendocrine aspects of the reproductive behavior involves a pol ysynaptic system, including the accessory olfactory bulb, the 'vomeron asal amygdala', the bed nucleus of the stria terminalis and medial pre optic and ventromedial hypothalamic nuclei. We found that 72 h after u nilateral transection of the vomeronasal nerves of rats an ipsilateral orthograde degeneration is seen in the neuropil of the medial preopti c, ventromedial, and arcuate hypothalamic nuclei. This represents an a natomical evidence of a monosynaptic link between the vomeronasal neur oepithelium and the medial preoptic nucleus, and hypothalamus.