Enhancements in swim stress-induced hypothermia, but not analgesia, following amygdala lesions in rats

Abstract

Lesions placed in the rat amygdala significantly reduce analgesic responses induced either by conditioning or exposure to a cat. Such lesions have alternatively reduced or failed to affect unconditioned foot shock analgesia. The present study expanded the situational determinants by examining whether lesions placed in the amygdala altered analgesia or hypothermia elicited by exposure to either continuous (CCWS) or intermittent (ICWS) cold-water swims. Lesion extent included the central, medial cortico-medial, baso-lateral, baso-medial and lateral amygdaloid nuclei. Basal jump thresholds, but not core body temperatures were significantly increased by unilateral and bilateral amygdala lesions. In contrast, the hypothermic, but not the analgesic responses following CCWS and ICWS were significantly enhanced by unilateral and bilateral amygdala lesions. These data support a hypothesis suggesting that these lesions are effective in reducing those classes of analgesic responses related to the signals of stressors than to the stressors themselves.