The noradrenergic system of the amygdala and aversive information processing

Water-deprived rats were trained to drink in a passive avoidance apparatus. After reaching a predetermined latency criterion, rats were given a single 3-sec, 3-mA footshock. Immediately or 12 hr after the footshock, rats were given intracranial injections of vehicular saline, norepinephrine (NE), propranolol, or dopamine (DA) into the amygdala, internal capsule, lateral ventricles, or caudate-putamen. Subjects were tested for passive avoidance at 30 min or 24 hr following footshock. No memory deficits were seen as a consequence of short-term retention or because of proactive or toxicity effects. Retention deficits were seen in the 24 hr test only in rats injected with NE in the amygdala, internal capsule, or lateral ventricles. However, qualitative differences in stress-indicative behaviors were noted in the NE groups and in the DA-amygdala animals. The results specifically suggest that the noradrenergic system of the amygdala is involved in the long-term processing of the emotional attributes of aversive information.