RESPONSES OF CA1 PYRAMIDAL NEURONS IS RAT HIPPOCAMPUS TO TRANSIENT FOREBRAIN ISCHEMIA - AN IN-VIVO INTRACELLULAR-RECORDING STUDY

The electrophysiological responses of CA1 pyramidal neurons to 5 min f orebrain ischemia were studied with intracellular recording and staini ng techniques in vivo. The baseline membrane potential rapidly depolar ized to approximately -20 mV about 3 min after the onset of ischemia a nd began to repolarize 1-3 min after recirculation. The amplitude of t his ischemic depolarization (ID) was related directly to the severity of ischemia and its latency of onset was inversely related to brain te mperature. Spontaneous synaptic activity ceased shortly after ischemia onset while the evoke synaptic potentials lasted until shortly before the onset of ID. Inhibitory postsynaptic potentials (IPSPs) disappear ed earlier than excitatory postsynaptic potentials (EPSPs) and the mem brane input resistance of CA1 neurons increased after the onset of isc hemia.