Effects of lesioning basal ganglia nuclei and output pathways on tremorine-induced tremor in rats

Abstract

The tremor produced by muscarinic cholinomimetics is believed to originate in the neostriatum but the efferent pathways are unknown. The intensity and frequency of tremor induced by tremorine was measured in the hindlegs of rats with unilateral basal ganglia lesions. A kainic acid lesion of one neostriatum reduced tremor intensity in the contralateral leg (CL). Unilateral electrolesions of the globus pallidus and nucleus accumbens had no effects on tremor. Both entopeduncular and subthalamic nuclei lesions reduced the frequency and intensity of tremorine tremor in the CL leg. The subthalamic lesion also increased tremor intensity and frequency in the ipsilateral leg. Lesions were made in some brain areas that receive basal ganglia efferent projections. Peak tremor intensity and frequency in both legs was greatly reduced by unilateral decortication. Unilateral lesions of the habenula, red nucleus and pedunculopontine nucleus had no effects on tremor intensity but reduced peak tremor frequency. Lesions of the substantia nigra and periaqueductal gray area had no effects on tremor. Unilateral removal of the superior colliculus reduced tremor intensity in both legs. The findings suggest that intensity and frequency of tremor are influenced by different basal ganglia efferent pathways; intensity involves strio-entopeduncular-cortical projections and frequency is determined by projections to midbrain and brainstem. The superior colliculus, with many muscarinic receptors, may be a direct target area for tremorine.