[Effect of high temperature on the direct cortical response]

Acute experiments were conducted on anesthetized cats placed in a thermochamber at a temperature of 45 degrees C. The direct cortical response in suprasylvian convolution of the cortex during hyperthermia and after the restoration of the thermal homeostasis was studied. It was revealed that hyperthermia caused primary inhibition at a temperature of 40 degrees C and above it, and even complete disappearance of the slow negative potential; above 43 degrees C there was found a gradual depression of the dendrite potential. Restoration of body normothermia following high hyperthermia was accompanied by an insignificant tendency to normalization of the slow negative potential parameters. Analysis of the dendrite potential changes on coupled stimuli testified to the fact that high temperature had a preponderant influence on the presynaptic elements of the cortical axodendrite synapses. On the basis of differential action of heat on the component composition of the direct cortical response a conclusion was drawn on the differences in the sensitivity of functionally different cells of the cortex during hyperthermia.