[The significance of the interstimulus time interval in repetitive paired applications of L-glutamate and acetylcholine for altering cortical neuronal reactivity].

Comparative analysis of the probability, direction and magnitude of changes of the mean firing rates for the background and L-glutamate--(Glu) and acetylcholine--(ACh) induced activity of single sensorimotor cortical neurons in the course of repeated separate and paired presentations of Glu and ACh was carried out in unanesthetized rats. A decline of Glu-induced activity was shown to be slower in a population of neurons affected by paired actions of Glu-ACh with 1.5 s time delay of ACh comparing with a decline of Glu-induced activity under the separate and paired applications with 3 s intervals. In the latter case the decrease of ACh-induced activity was more pronounced and the probability of the increase of the background activity was lower than in the course of the isolated presentations of ACh. It is suggested that interstimulus time interval determines the type of changes of neuron responsiveness.