beta-Adrenergic manipulation in amygdala central n. alters rabbit heart rate conditioning

The present study was conducted to assess the effects of beta-adrenergic manipulation within the central nucleus of the amygdala on Pavlovian heart rate conditioning in the rabbit. Administration of the beta-adrenergic antagonist dl-propranolol into the central nucleus impaired the acquisition of conditioned heart rate responding compared to a vehicle injected control group. No significant effects of dl-propranolol on either baseline heart rate or on the heart rate orienting response were observed. The effect of dl-propranolol on conditioning exhibited stereospecificity, and animals receiving combined intracerebral injections of dl-propranolol and the beta-adrenergic agonist 1-isoproterenol did not exhibit comparable conditioning impairments. In addition, dl-propranolol administration dorsal to the central nucleus or into amygdala sites anterior or posterior to the central nucleus was less effective. These results support the interpretation that beta-adrenergic activity within the central nucleus region of the amygdala complex contributes to the acquisition of classically conditioned heart rate responding.