Intra-amygdala kinase inhibitors disrupt retention of a learned avoidance response in rats

To assess the involvement of intra-amygdala kinase activity in aversively motivated learning, rats received intracranial injections of polymixin B sulfate (PMXB)--a protein kinase C (PKC) and calcium/calmodulin-dependent kinase II inhibitor--immediately after inhibitory avoidance training. When tested 48 h later, retention was significantly impaired relative to vehicle-injected controls. Delayed injections (2 h posttraining) and injections made dorsal to the amygdala were ineffective. Immediate posttraining injections of the more selective PKC inhibitor, NPC 15437, also impaired retention. These results suggest that intra-amygdala protein phosphorylation must occur soon after training for learned avoidance responses to be successfully retained.