Calmodulin-dependent Kinase Kinase/calmodulin Kinase I Activity Gates Extracellular-regulated Kinase-dependent Long-term Potentiation Intracellular Ca 2ϩ and Protein Phosphorylation Play Pivotal Roles in Long-term Potentiation (ltp), a Cellular Model of Learning and Memory. Ca 2ϩ Regulates Multiple