Dynamics of the reactivity of cortical neurons to the repeating isolated action of L-glutamate and acetylcholine.

A comparative analysis of the probability, directionality, and intensity of the changes in the average frequency of the baseline (BIA) and L-glutamate-induced (GlIA) and acetylcholine-induced (AChIA) impulse activity of individual neurons of the sensorimotor cortex of unanesthetized rats showed that the reactions to Gl are most variable; this is expressed in a significantly higher percent of neurons with potentiation of responses to Gl as compared with the proportion of cells which manifested an increase in the AChIA in the course of 20 applications of the mediators. As a result of 100 applications, the GlIA decreases most frequently; also, the degree of decrease in GlIA over the entire duration of the testing exceeds the degree of decrease in AChIA. It is more characteristic of ACh than of Gl to increase the level of BIA in the periods between the reactions to ACh, while in the case of repeated application of Gl, dynamics of decrease in BIA are characteristic. The results are discussed from the perspective of a possibly different functional role of the glutamatergic and cholinergic neuromediator systems in the cerebral cortex in the process of formation of the dynamics of neuronal activity during learning.