[Glutamatergic excitation of cortical neurons depending on site of origin on the neuronal membrane and cholinergic regulation under hypothermic condition].

In sensorimotor cortical slices of guinea pig in the course of cooling of incubating fluid from 34 to 21-22 delta C it was shown that hypothermia does not influence on the evoked spike reactions to iontophoretic application of glutamate to the soma, but glutamate action on the dendritic locus causes the shot latency somatic spike response during hypothermic increasing of the rate of spontaneous activity and long latency spike response--during hypothermic fall of activity. While the cooling rate of spontaneous activity in the slow firing neurons was mainly increasing and in the high firing neurons (above 4 spikes per second)--decreasing. The changes in spontaneous activity began at 30 degrees C along with the decreased spike reactions to iontophoretic applications of acetylcholine and efficacy of dendro-somatic propagation. At the same temperature the fall of spike amplitude was initiated and increased with further hypothermia. It is proposed that the basis for hypothermic changes of neuronal activity.is the decreased rate of M-cholinergic process at 27-29 degrees C. Neurons of different physiological properties display different sensitivity to hypothermic factor.