Temporal specificity in the action of stimuli during the formation of associative ultrastructural reorganizations in neurons of the cerebral cortex.

A morphometric investigation of various components of the synapses of neurons of the sensorimotor region of the cerebral cortex of rats with different variants of combined and uncombined repeated microiontophoretic application of glutamate and acetylcholine has been carried out. A substantial dependence of the character and expressivity of the reorganizations of the thickness of the postsynaptic density (PSD), of the width of the synaptic cleft, and the length of the active zone of the synapses, on the temporal relationships in the action of mediators has been identified: significant changes in the thickness of the PSD appeared only with the combined applications of the stimuli (neuromediators); the maximum thickening of the PSD was induced by the combined action of glutamate and acetylcholine with a 3-second delay in the latter. A hypothesis is presented according to which the temporal specificity in the integration of associable signals arriving at neurons is determined by the kinetics of the various interacting biochemical regulator mechanisms.