EFFECT OF HYPOTHERMIA ON EXCITABILITY OF SPINAL NEURONS

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Abstract
The effects of hypothermia on accommodation in neurons of the central nervous system were determined. Intracellular recording of neuron responses was used. Single motoneurons and interneurons of the spinal cord of cats anesthetized by Nembutal were stimulated directly by currents applied through a microelectrode. By modifying the rate of rise of linearly increasing current strengths it was possible to determine the minimal gradient required for stimulation. It was found that during hypothermia the rate of current rise required for stimulation was less than at normal temperatures. Rewarming of the cord restored, with some hysteresis, the control minimal gradient. This observed greater effectiveness of slowly rising current strengths during hypothermia was ascribed to loss of accommodation. It was felt that this contributed to the hyper-responsiveness and repetitive firing occurring during certain phases of central nervous system cooling.