Ensity, optimally positioned to sense the transient Ca2 elevation. PKA seems to be a key mediator of LTP induction in young animals, whereas CaMKII is necessary and sufficient for early-phase NMDA receptor-dependent LTP in older animals. Roles for the atypical PKC isoform PKM , the nonreceptor tyrosine kinase src, and nitric-oxide synthase have been described previously (Pelkey and McBain, 2008).