Central Processing of Chemosensory Signals

Florida State University, Tallahassee FL

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Abstract

The Medial Amygdala is important for control of sexual and emotional behavior. Chemosensory information is sent directly to the anterior part of the medial amygdala predominantly via the accessory olfactory system, with small inputs from the main olfactory bulb. In male hamsters, chemosensory information about biologically relevant natural stimuli is detected via receptors in the vomeronasal organ. Information is passed initially to the accessory olfactory bulb (AOB), then to the anterior medial amygdala (MeA), which projects to the posterior medial amygdala (MeP). The pathway from MeA provides the majority of chemosensory input to MeP. Artificial or socially irrelevant stimuli increase neuronal activity in the initial parts of the vomeronasal pathway, as measured by increased Fos expression, but information is not passed on to the posterior part of the amygdala. Natural, socially relevant stimuli activate the initial regions (AOB and MeA), but also the posterior medial amygdala, which is abundant in steroid receptors. Many social behaviors are dependent on an adequate steroid level. These data suggest that the MeA ay act to filter patterns of input that have different social relevance to animals. The goal of this proposal is to determine the mechanisms of inhibition in the intra-amygdaloid circuits involved with the integration of sensory input from the accessory olfactory system and social relevance to the animal.