EXCITABILITY OF CORTICAL AFFERENT SYSTEMS DURING BARBITURATE ANESTHESIA

Abstract

Excitability in the somesthetic pathway was studied in cats under Na pentobarbital anesthesia. Absolutely unresponsive periods were found to be greatly lengthened as anesthesia was deepened, and the effect was reversed during recovery. No subnormal or supranormal periods were detected. The excitability curve is depressed by thalamo-cortical after-discharge, by the "burst" activity characteristic of barbiturate anesthesia, and by certain spontaneous rhythms occurring under light anesthesia. These 3 types of activity are consequently believed to travel at least partly in neurones of the somesthetic pathway. The disappearance of these rhythms in deep anesthesia may result from the anesthetic process which lengthens unresponsiveness in the thalamus.