A comparison of LTP in wild-type mice and mice in which PKA has been compromised by the expression in the hippocampus of a transgene, a dominant negative inhibitor of PKA. This inhibitor R(AB) is a mutated form of the regulatory subunit of PKA that inhibits the catalytic subunit but does not recognize cAMP. Two lines of mutant mice (R(AB)-1 and R(AP)-2) are compared to the wild-type mice (WT). The mutant mice have perfectly good early LTP comparable to that of wild type mice. Mutations in mice that block PKA reduce or eliminate late LTP.