57 - Sexual Differentiation of Mammalian Olfactory Communication

Abstract

A consensus is emerging that both the accessory and main olfactory systems (only the main olfactory in Old World primates) mediate the effects of pheromones on social interaction in mammalian species. We review evidence showing that morphological and functional sex differences occur at each level of the accessory olfactory system, beginning with the vomeronasal organ and extending to the subdivisions of the medial amygdala and hypothalamus that receive inputs from the vomeronasal organ-accessory olfactory bulb. We argue that the best-available evidence suggests that in both sexes accessory olfactory inputs control subjects' motivation to approach opposite-sex pheromones, whereas sex discrimination, like individual recognition, depends on the processing of pheromones by the main olfactory system. Whereas there is little evidence of morphological sexual dimorphism in the main olfactory system, there is evidence that the function of this system in detecting and processing pheromones is sexually differentiated in numerous mammalian species including man. Finally, evidence is reviewed suggesting that in mice the main olfactory system provides inputs to the accessory olfactory bulb – accessory olfactory system that respond selectively to opposite-sex pheromonal cues.