Intracellular recording during focal hypothermia in cat pericruciate cortex

Abstract

Intracellular records were obtained from both glia and neurons in cat pericruciate cortex during focal hypothermia induced by a Peltier device. Glial membrane potential varied inversely and linearly with temperature. For 28 glia, the mean depolarization was 16.8 ± 7.0 mv for a temperature decrement of 5–6 C. Glial input resistance varied inversely and reversibly with temperature with a Q 10 of 2.5. Neuronal membrane initially hyperpolarized 4.5 ± 3.3 mv until 3 min after the temperature decreased below 30 C. At that temperature and time a plateau depolarization occurred with a magnitude of 14.7 ± 5.5 mv. During rewarming, the membrane again hyperpolarized 5.9 ± 4.0 mv with return to precool values on complete rewarming. Action potential firing patterns also changed with hypothermia. The regular firing pattern was supplanted by a doublet, triplet, and quadruplet mode during the period of initial hyperpolarization. Tonic firing occurred on the upramp of the plateau depolarization and the multiple spike mode returned during the postcool hyperpolarization. Models are proposed to explain the glial depolarization with hypothermia as a result of decreased glial NaK pumping with a resultant increase in extracellular K. Neuronal hyperpolarization was a result of accelerated electrogenic NaK pumping in response to the increasing extracellular K. The tendency to the multiple spike mode is explained as a result of quantitative differences in somatic-dendritic interactions.