ROLE OF NA-K PUMP POTASSIUM REGULATION AND IPSPS IN SEIZURES AND SPREADING DEPRESSION IN IMMATURE RABBIT HIPPOCAMPAL SLICES

Using the immature (8-12 days postnatal) rabbit hippocampal slice preparation, we investigated regional extracellular potassium concentration ([K+)(o)) changes that occur during spontaneous and evoked spreading depression (SD) episodes. We report here a difference between the CA1 and CA3 cell populations in the immature hippocampus with regard to 1) resting [K+](o), 2) magnitude of the [K+](o) change during seizurelike events and SDs, and 3) susceptibility to SD episodes. Experiments were also performed to elucidate the roles that the Na-K pump and synaptic inhibition play in controlling SD onset, duration, and recovery. We demonstrated a major role for potassium regulation by the Na-K pump and a lesser modulatory role for inhibitory postsynaptic potentials (IPSPs) in preventing SD in the CA3 region.