Effect of catecholaminergic transmission deficiency upon neuronal responses of the ventrolateral thalamic nucleus evoked by stimulation of cerebellar and pallidal inputs

Abstract

Neuronal responses of the ventrolateral thalamic nucleus (VL) to the afferent stimulation were studied in chronic experiments on cats before and after injection of haloperidol and droperidol in cataleptic doses. As distinct from the reactions of intact animals, after injection of neuroleptics the initial excitative VL neuronal responses to the cerebellar stimulation were characterized by the irregularity of manifestation and the variability of the latent period, the responses in the form of burst discharges appeared. During pallidal stimulation a statistically significant increase in the number of initial inhibitory responses consisting of two periods of the background activity suppression with an excitation phase separating them was observed, while monophase inhibitory reactions prevailed (68%) in intact animals. Under neuroleptics the reactions with rhythmic alternation of excitative and inhibitory periods of the impulsive activity with frequency 3-5/s. occurred. It is suggested that revealed peculiarities of the neuronal reactions result from the hyperpolarizing state of the VL neurons because of the augmented external inhibitory actions due to a blockade of dopamine receptors of the nigrostriatal system or because of the reduced depolarizing influences under the break of the central alpha-adrenergic transmission.