The action potential (Na~+ spike) of neurons is often followed by a compound after hyperpolarization (AHP) which is mediated by Ca~(2+)-dependent K~+ channels. Pyramidal cells in the cerebral cortex are known to have fast, medium and slow AHPs. It is commonly accepted that the fast AHP (fAHP) is mediated by a kind of C- or BK-K~+ channels. The fAHP is characterized by a short duration of about 20 ms, its remarkable voltage dependence and sensitivity to low concentration (<1 mmol/L) of Tetraethylammonium (TEA).The mAHP results from activation of AHP- or SK-K~+ channels and has a long duration over 200 ms. It is poorly voltage-dependent and blocked by Apamin, but not by TEA. Several The action potential (Na ~ + spike) of neurons is often followed by a compound after hyperpolarization (AHP) which is mediated by Ca ~ (2 +) - dependent K ~ + channels. Pyramidal cells in the cerebral cortex are known to have fast , medium and slow AHPs. It is more accepted that the fast AHP (fAHP) is mediated by a kind of C- or BK-K ~ + channels. The fAHP is characterized by a short duration of about 20 ms, its remarkable voltage dependence and the sensitivity to low concentration (<1 mmol / L) of Tetraethylammonium (TEA) .The mAHP results from activation of AHP- or SK-K ~ + channels and has a long duration over 200 ms. It is poorly voltage-dependent and blocked by Apamin, but not by TEA