THE ROLE OF INTERSTIMULUS TIME-INTERVAL I N THE REPEATED PAIRED APPLICATIONS OF L-GLUTAMATE AND ACETYLCHOLINE FOR THE CHANGES IN THE REACTIVITY OF NEURONS IN THE CEREBRAL-CORTEX

Comparative analysis of the probability, direction and magnitude of ch anges of the mean firing rates for the background and L-glutamate - (G lu) and acetylcholine - (ACh) induced activity of single sensorimotor cortical neurons in the course of repeated separate and paired present ations of Glu and ACh was carried out in unanesthetized rats. A declin e of Glu-induced activity was shown to be slower in a population of ne urons affected by paired actions of Glu-ACh with 1,5 s time delay of A Ch comparing with a decline of Glu-induced activity under the separate and paired applications with 3 s intervals. In the latter case the de crease of ACh-induced activity was more pronounced and the probability of the increase of the background activity was lower -than in the cou rse of the isolated presentations of ACh. It is suggested that interst imulus time interval determines the type of changes of neuron responsi veness.