Intracellular recording from CA1 neurons confirmed that short periods of anoxia (95% N2 + 5% CO2 for 2-4 min) have a hyperpolarizing action, caused by a rise in K conductance. After blockage of K channels with extracellular Cs+ and tetraethylammonium (or intracellular Cs+), large inward currents of Ca were evoked by depolarizing pulses: transient currents at a holding potential near -70 mV, and more sustained ones near -50 mV. Both types of Ca current were much reduced or fully suppressed after 1-3 min of anoxia, but they largely (or fully) recovered within 1-10 min of starting reoxygenation.