The amygdala is necessary for the expression of conditioned but not unconditioned analgesia.

Abstract

Lesions of the basolateral region and central nucleus of the amygdala prevent conditioned analgesia (Helmstetter, 1992). In general, these regions of the amygdala are more critically involved in the expression of conditioned reactions to aversive events than in the mediation of unconditioned reactions. The impact of amygdala lesions on both conditioned and unconditioned analgesia was explored in Sprague-Dawley rats. The lesions completely prevented the expression of conditioned analgesia, but had no effect on unconditioned analgesia.