Potassium currents in CA1 neurons of rat hippocampus increase shortly after transient cerebral ischemia.

Total potassium current in CA1 pyramidal neurons was studied using whole-cell voltage-clamp recording technique in hippocampal slices prepared before and at 6-8 h after transient forebrain ischemia. The total potassium current significantly increased from a control value of 2.17+/-0.17 to 2.96+/-0.31 nA (measured at +70 mV, P<0.05) after ischemia. The slope factor V(c) of activation curve significantly decreased and the half-inactivation voltage V(h) shifted to more depolarized potentials after ischemia. These results indicate that the increase of potassium current might be responsible for the decreased excitability in CA1 neurons after severe ischemia and may be involved in postischemic cell death in hippocampus.