Calcium-stimulated adenylyl cyclase activity is critical for hippocampus-dependent long-term memory and late phase LTP

It is hypothesized that Ca²⁺ stimulation of calmodulin (CaM)-activated adenylyl cyclases (AC1 or AC8) generates cAMP signals critical for late phase LTP (L-LTP) and long-term memory (LTM). However, mice lacking either AC1 orAC8 exhibit normal L-LTP and LTM. Here, we report that mice lacking both enzymes (DKO) do not exhibit L-LTP or LTM. To determine if these defects are due to a loss of cAMP increases in the hippocampus, DKO mice were unilaterally cannulated to deliver forskolin. Administration of forskolin to area CA1 before training restored normal LTM. We conclude that Ca²⁺- stimulated adenylyl cyclase activity is essential for L-LTP and LTM and that AC1 or AC8 can produce the necessary cAMP signal.