Study on the role of the endopirifiorme nucleus and the anterior part of the basolateral nucleus of the amygdala in the predatory, contextual and exploratory fear behavior in a new environment

Abstract

The basolateral nucleus of the amygdala is usually study as the combination of both the lateral nucleus (LA) and basolateral (BLA). The role of BLA and LA in the expression and acquisition of conditioned fear to a painful stimulus has been extensively studied. Experiments conducted in our laboratory confirm that animals with bilateral lesions in the LA show a decrease of innate fear response and abolish contextual fear response to predatory threat. In contrast, preliminary data indicate that bilateral lesions affecting only the anterior part of the BLA (BLAa) apparently does not affect innate responses neither it affects contextual fear responses to predator. Interestingly, BLAa injuries appear to markedly decrease the anxious behavior during exploration of a new environment. Thus, the first objective of our work is to extend our preliminary data examining systematically (with bilateral cytotoxic lesions and restricted to the nuclei) the role of the BlAa in the innate and contextual responses to predatory threat, as well as their involvement in anxious behaviors observed during the familiarization period to a new environment. Preliminary data from our laboratory also indicate that bilateral lesions restricted to the endopiriform nuclei abolished fear responses observed in context previously associated with the predator, but did not change the innate fear responses during predatory exposure. However, in contrast to what is observed in animals with bilateral lesion BLAa, injury in the endopiriform does not affect anxious behaviors observed during exposure to a new environment. Thus, in the second part of this research project we will expand our preliminary data examining systematically (with bilateral cytotoxic lesions restricted to the region) the role of the endopiriform in the innate and contextual responses to predatory threat, as well as their involvement in anxious behaviors observed during the familiarization period to a new environment. (AU)