Changes in the activity of ventrolateral thalamic neurons and instrumental response after systemic administration of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Neuronal activity in the ventrolateral thalamus during execution of instrumental reaction before and after parenteral administration of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was investigated in samples of 81 and 70 cells, respectively. After a 5-day course of one 5 mg/kg MPTP injection daily, firing rate of neurons in which activity correlated with forelimb movement rose significantly; this activation increased in length during the initial, flexor, and extensor stages of motor response. Bradykinesia set in together with intensified neuronal activation in the animals. Microinjection of exogenous dopamine into the caudate nucleus brought about correction of motor disturbance and a reduced neuronal firing rate in the ventrolateral (thalamic) nucleus. It was deduced that the nigrostriatal system exercises inhibitory control over the activity of thalamic neurons associated with forelimb movement in thalamic neurons in intact animals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 3, pp. 291–300, May–June, 1990.