Inhibition and excitation of neck and shoulder muscles during unilateral electrical stimulation of the rat neostriatum.

Electrical stimulation of the caudate-putamen (Cd-Pt) in anesthetized adult male rats was used to determine the nature and extent of the control exerted by the Cd-Pt over the following neck and shoulder muscles: the trapezius, biventer cervicis, rectus capitis and scalenus dorsalis. Unilateral Cd-Pt stimulation resulted in a pattern of muscle responses marked by immediate inhibition of ipsilateral spontaneous activity and subsequent excitation of contralateral activity. Lesions of the substantia nigra pars reticulata blocked the excitation in 3 of the 4 muscles, while globus pallidus lesions had equivocal results. However, control ablations of the frontoparietal motor cortex, which blocked excitation in all muscles, and kainic acid lesions of the Cd-Pt, which had no effect on excitation, suggested that the excitation of muscle activity can only be attributed to the stimulation of corticofugal fibers passing through this region (i.e. the Cd-Pt). The inhibition of spontaneous activity does appear to be attributable to stimulation of the Cd-Pt.