Effects of lesions in some basal ganglia nuclei and efferent projections on tremorine-induced limb rigidity in rats

A mechanical apparatus was used to measure in rats the effects of some unilateral basal ganglia lesions on the hind-limb rigidity produced by the cholinomimetic compound, tremorine. A globus pallidus lesion reduced the resting tone and greatly increased rigidity in the contralateral leg. Lesions in the entopeduncular, subthalamic, and accumbens nuclei had no effects on rigidity, although the entopeduncular nucleus lesion reduced resting limb tone. The role of the globus pallidus in rigidity is significant in relation to work in which striatal lesions abolished tremorine-induced rigidity. Some brain regions that receive basal ganglia efferent fibers received a lesion unilaterally. Lesions in the substantia nigra, red nucleus, or pedunculopontine nucleus had no effect on tremorine-induced rigidity. A habenular lesion significantly reduced rigidity in both hind legs. Very pronounced reductions in rigidity occurred after midbrain lesions involving the central periaqueductal grey region and the superior colliculus. The basal ganglia output pathways that may mediate tremorine rigidity are discussed, together with the possibility that the superior colliculus, which has many muscarinic receptors, may be influenced directly by tremorine.