Effect of Pentobarbital and Ether on the Spreading Cortical Depression

Abstract

A spreading depression of cortical activity is elicited in the rabbit by weak faradic stimulations of the cerebral cortex. The depression is accompanied by a slow potential change, during which the cortex first turns negative, then positive with respect to an indifferent electrode. This slow potential change is not abolished by pentobarbital even in very large doses (200 mg./kg. body wt. distr. over 4 injns.). The spontaneous electrocorticogram was abolished by smaller doses of pentobarbital (about 50 mg./kg. body wt.). Ether in a concn. of 7%, administered in the respiratory air, decreased and sometimes abolished the spreading slow potential change. In a concn. of 10%, ether always abolished the spreading slow potential change. A small potential change in the immediatevicinity of the stimulating electrodes could then be recorded. Under these conditions considerable spontaneous cortical activity was still present. The effects of ether and of pentobarbital on the slow potential change accompanying the spreading depression, are strikingly parallel to the effects of these narcotics on depolarization potentials which can be led off from the spinal cord during asphyxiation.