ALPHA-ISOFORM OF CALCIUM-CALMODULIN DEPENDENT PROTEIN-KINASE-II (CAM-II KINASE-ALPHA) RESTRICTED TO EXCITATORY SYNAPSES IN THE CA1 REGION OF RAT HIPPOCAMPUS

Pre-embedding immunoperoxidase staining for CAM II kinase-alpha and po st-embedding immunogold staining for glutamate and GABA, were used to reveal the subcellular distribution of CAM II kinase-alpha at transmit ter-characterized synapses in the CA1 region of rat hippocampus. Immun oelectron microscopy showed that the majority of CAM II kinase-alpha-i mmunostained neuronal profiles were dendritic spines presumably derive d from pyramidal cells. CAM II kinase-alpha immunoreactivity was mainl y localized in postsynaptic densities associated with glutamatergic ax on terminals. No CAM II kinase-alpha immunoreactivity was detected in GABA-immunoreactive profiles or at GABAergic synapses. This study prov ides morphological evidence that CAM II kinase-alpha is involved only in excitatory neuronal transmission in the CA1 region. The enzyme is u nlikely to be involved in plasticity at GABA synapses.