SEX-DIFFERENCES IN THE VOMERONASAL SYSTEM

In the early eighties we found sex differences in the vomeronasal orga n (VNO) and hypothesized that the vomeronasal system (VNS), a complex neural network involved in the control of reproductive behavior, might be sexually dimorphic. At that time sex differences had already been described for some structures that receive VNO input, such as the medi al amygdala, the medial preoptic area, the ventromedial hypothalamic n ucleus, and the ventral region of the premammillary nucleus. Since the n, we have shown sex differences in the accessory olfactory bulb (AOB) , the bed nucleus of the accessory olfactory tract (BAOT), and the bed nucleus of the stria terminalis (BST), When new VNS connections were found, all of them ended in nuclei that present sex differences, In ge neral, sex differences in the olfactory system show two morphological patterns: one in which males present greater morphological measures th an females, and just the opposite, To explain the morphometric measure s of males in the latter, it has been hypothesized that androgens serv e as inhibitors. Our work on the involvement of the GABA(A) receptor i n the development of AOB and maternal behavior sex differences also su ggests that neonatal changes in neuronal membrane permeability to the ion Cl- differences. This might be the first animal model to help us t o understand the situation in which human genetic and gonadal sex do n ot agree with brain and behavioral sex, Finally, we stress that sex di fferences in the VNS constitute a neurofunctional model for understand ing sex differences in reproductive behaviors. (C) 1997 Elsevier Scien ce Inc.