The activity of neurons of the V layer was recorded extracellularly in slices of guinea pig parietal cortex. We studied the spontaneous activity and responses of neurons to iontophoretic application of acetylcholine in the temperature range from 25 to 36 °C. The impulse responses induced by acetylcholine and the frequency of spontaneous activity had similar dynamics with an increase in the temperature of the incubation medium. We found two temperature zones where the efficacy of cholinergic responses rapidly transited to a higher level: 27-29°C and 34-36°C. The average gradient of cholinergic response was over 200% per 1 degree in the second zone of transition. The high efficacy of the cholinergic response at 35-36°C was accompanied by a significant decrease in the amplitude of spikes of cortical neurons, which indicated the onset of the hypoxic state determined by artificial incubation.