Brief anoxic episodes induce long-lasting changes in synaptic properties of rat CA3 hippocampal neurons

The effects of brief anoxic episodes on rat CA3 hippocampal neurons were studied with intracellular and extracellular techniques in the in vitro slice preparation. After repeated (3-7 times), brief (2-6 min duration each) applications of artificial cerebrospinal fluid (ACSF) saturated with 95% N2 and 5% CO2, electrical stimulation of various inputs to CA3 neurons, evoked an excitatory postsynaptic potential (EPSP) followed by an all-or-none burst. This response which persisted for several hours after the last anoxic episode, is reminiscent of the bursts induced by various convulsive agents. Post anoxic bursts are generated by a polysynaptic network which converge on the apical distal segment of CA3 neurons. It is concluded that a repetitive impairement of metabolism produces long lasting changes in the synaptic properties of CA3 neurons.