Mild hypothermia protects rat hippocampal CA1 neurons from irreversible membrane dysfunction induced by experimental ischemia

In order to examine the effects of hypothermia on the changes in membrane potential induced by experimental ischemia (deprivation of oxygen and glucose), intracellular recordings were made from single CA1 pyramidal neurons in slice preparations of rat hippocampus. Application of ischemic medium caused irreversible changes in membrane potential consisting of an initial hyperpolarization, then a slow depolarization and a rapid depolarization. Al temperatures of 35 degrees C and 37 degrees C, once the rapid depolarization occurred, readministration of oxygen and glucose failed to restore the membrane potential, a state referred to as irreversible membrane dysfunction. When the temperature was lowered to between 27 degrees C and 33 degrees C, the membrane potential returned to the control resting membrane potential in 75% of the neurons. The temperature coefficients (Q(10)) of the latency, the amplitude, and the maximal slope of the rapid depolarization were 2.5, 1.4 and 2.9, respectively. II is concluded that the critical neuroprotective temperature in ischemia-induced membrane dysfunction is found to be 33 degrees C in single CA1 neurons in vitro. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.