The cholinergic inhibition of afterhyperpolarization in rat hippocampus is independent of cAMP-dependent protein kinase

The possible involvement of protein kinase A (PKA) in the muscarinic inhibition of the slow afterhyperpolarizing current ( I AHP) was investigated in rat hippocampal pyramidal cells. I AHP was recorded using the whole cell method in hippocampal slices, and Rp-cAMPs, a PKA antagonist, was applied intracellularly. The inhibition of I AHP by carbachol was not affected by Rp-cAMPS. In contrast, Rp-cAMPS reduced the cAMP-dependent inhibition of I AHP by norepinephrine. The results show that phosphorylation by PKA does not contribute to the muscarinic effect on I AHP.