ALTERATIONS IN INTRALAMINAR AND MOTOR THALAMIC PHYSIOLOGY FOLLOWING NIGROSTRIATAL DOPAMINE DEPLETION

The response of central median/central lateral (CM/CL) and ventral ant erior/ventral lateral (VA/VL) thalamic neurons to tactile sensory stim ulation of the face and electrical stimulation of the striatum was ass essed in awake cats before and after 1-methyl-4-phenyl- 1,2,3,6-tetrah ydropyridine (MPTP) exposure. When cats exhibited Parkinson-like motor deficits, there was a significant decrease in the number of CM/CL and VA/VL neurons responsive to tactile stimulation of the face. Mean spo ntaneous firing rates decreased by 58% in the CM/CL nuclei, 65% in the VA, and 49% in the VL. The number of thalamic neurons responding to e lectrical stimulation of the striatum was also significantly decreased in parkinsonian animals. Approximately 6 weeks after MPTP exposure, w hen cats had spontaneously recovered gross motor function, thalamic re sponses to peripheral sensory stimulation, electrical stimulation of t he CD, and spontaneous activity rates, returned to approximately norma l levels in all thalamic areas studied. These findings support the con cept that abnormalities in the transmission of information through the thalamus, and in particular, a decrease in sensory responsiveness in intralaminar and motor thalamic regions subsequent to nigrostriatal do pamine depletion, may contribute to the generation of Parkinson-like m otor and sensorimotor deficits.