Central amygdala lesions affect behavioral and autonomic balance during stress in rats.

The effects of a bilateral electrolytical lesion of the CEA on the behavioral and sympathetically induced cardiac response in the shock-probe/defensive-burying test have been analyzed in male Wistar rats. Lesions in the CEA failed to affect defensive burying and accompanying tachycardiac response as compared to sham-lesioned controls during the presentation of the electrified shock probe (unconditioned test). However, CEA lesioning attenuated the bradycardiac response and the immobility behavior during the late part of the test. Retention of this behavior one day after the exposure to the probe (conditioned test) was attenuated by the lesion. However, when the lesion was placed after the unconditioned test situation, retention of the burying was not affected, but the animals failed to show immobility behavior. These results, in agreement with former studies, suggest that the CEA is involved particularly in the organization and/or expression of the passive component of the behavior and the parasympathetic outflow during stress. The active component, i.e., burying behavior, and the accompanying tachycardiac response remains unaffected unless the acquisition of the stress response took place with damaged CEA.