Inhibitory avoidance learning alters the amygdala calcium/calmodulin-dependent protein kinase II activity in rats

This study investigated the role of amygdala CaM-kinase II (calcium/calmodulin-dependent protein kinase II) in affective learning and memory. In Experiment I, two groups of rats were trained on a one-trial step through inhibitory avoidance learning task. The experimental group received a high intensity foot shock contingent upon the stepping-through behavior, whereas the control group received a series of non-contingent low intensity foot shock during training. The experimental rats showed significantly higher retention scores than the control rats. Correspondingly, rats in the experimental group showed significantly higher Ca2+-independent activity of CaM-kinase II than the controls. Intra-amygdala injection of a specific CaM-kinase II inhibitor, KN-62, before the training trial disrupted affective learning. In comparison with the vehicle-injected controls, pretraining injection of KN-62 impaired the acquisition of affective specific learning. These results, taken together, indicated that the activation of amygdala CaM-kinase II in the amygdala is associated with the affective learning behavior, and may be one of the neural mechanisms underlying formation of affective memory.