Intracellular injection of a Ca2+ chelator inhibits spike repolarization in hippocampal neurons.

The Ca-dependence of spike repolarization and afterhyperpolarizations (AHPs) in Ca1 pyramidal cells, was tested with intracellular electrodes containing the Ca buffers EGTA or 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). EGTA blocked only the slow AHP; but the fast-acting Ca chelator BAPTA also inhibited spike repolarization and the fast AHP. This supports the hypothesis that a fast Ca-activated'K-current contributes to spike repolarization.