SPATIAL-LEARNING ALTERS HIPPOCAMPAL CALCIUM CALMODULIN-DEPENDENT PROTEIN-KINASE-II ACTIVITY IN RATS

This study investigated the role of hippocampal CaM-kinase II (calcium /calmodulin-dependent protein kinase II) in spatial learning. In Exper iment I, three groups of rats received 1, 2 or 5 days of training on a spatial task in the Morris water maze with a hidden platform, while a control group was trained on a nonspatial task with a visible platfor m. The acquisition rate in the spatial task was slower than that in th e nonspatial task. However, rats receiving 5 days of spatial training had the highest Ca2+-independent activity of CaM-kinase II compared wi th the controls;receiving nonspatial training and rats having 1 or 2 d ays of spatial training. Furthermore, the level of hippocampal Ca2+-in dependent CaM-kinase II activity was correlated with the final perform ance on the spatial task. In Experiment II, rats received intra-hippoc ampal injections of a specific CaM-kinase II inhibitor - KN-62 - befor e each training session. In comparison with the vehicle-injected contr ols, pretraining injection of KN-62 retarded acquisition in the spatia l task but had no effect on the nonspatial task. These results, taken together, indicated that the activation of CaM-kinase II in the hippoc ampus is not only correlated to the degree of spatial training on the Morris water maze, but may also underlie the neural mechanism subservi ng spatial memory.