Descending supraspinal effects under conditions of disturbance of the inhibitory processes in the nuclei of the medulla: The formation of the generators of excitation

Abstract

The descending effects produced by stimulation of the fastigial nucleus of cerebellum and the neuronal activity in the nuclei of the medulla were studied on cats under light Nembutal-chloralose anesthesia or on decerebrated animals at various times following injection of tetanus toxin. The latter was used as an agent producing suppression of the inhibitory processes. A significant enhancement of the descending facilitation of extensor monosynaptic reflexes after injection of tetanus toxin into the lateral vestibular nucleus was established, and of the descending inhibition of polysynaptic reflexes following injection of tetanus toxin into the gigantocellular nucleus. The characteristic feature was the reducing of latent periods of the descending effects, their abrupt increase up to maximum, and a significant lengthening of their duration. The poisoned nuclei showed an increase in amplitude and frequency of discharges in the integral background, and especially in evoked activity, and augmented number of neurons with cluster activity. The enhanced background activity in the examined areas of poisoned nuclei could be temporarily suppressed by strong direct electrical shock or injection of glycine into these regions. The obtained data suggest that the disturbance of the inhibitory processes in complex relay nuclei represents a condition contributing to formation in the latter of the generators of pathologically enhanced excitation. The mechanisms of formation and characteristic features of the activity of generators and their role in pathology of the nervous system are discussed. Also considered is the modeling of neurological syndromes by way of creation of generators of pathologically enhanced excitation in various regions of the CNS.