PERSISTENT ACTIVATION OF THE ZETA-ISOFORM OF PROTEIN-KINASE-C IN THE MAINTENANCE OF LONG-TERM POTENTIATION

Long-term potentiation in the CA1 region of the hippocampus, a model f or memory formation in the brain, is divided into two phases. A transi ent process (induction) is initiated, which then generates a persisten t mechanism (maintenance) for enhancing synaptic strength. Protein kin ase C (PKC), a gene family of multiple isozymes, may play a role in bo th induction and maintenance. In region CA1 from rat hippocampal slice s, most of the isozymes of PKC translocated to the particulate fractio n 15 sec after a tetanus. The increase of PKC in the particulate fract ion did not persist into the maintenance phase of long-term potentiati on. In contrast, a constitutively active kinase, PKM, a form specific to a single isozyme (zeta), increased in the cytosol during the mainte nance phase. The transition from translocation of PKC to formation of PKM may help to explain the molecular mechanisms of induction and main tenance of long-term potentiation.