APPEARANCE OF EMG ACTIVITY AND MOTOR ASYMMETRY AFTER UNILATERAL LESIONS OF THE DOPAMINERGIC INNERVATION TO THE SUBTHALAMIC NUCLEUS IN THE RAT

The effects of unilateral injections of 6-hydroxydopamine into the sub thalamic nucleus on muscular rigidity and on motor behavior were exami ned. Muscular rigidity was judged by the appearance of electromyograph ycal activity in the gastrocnemius-soleus muscle and motor behavior by the turning induced by DL-methamphetamine. The unilateral injection o f 6-hydroxydopamine produced the appearance of electromyographycal act ivity ipsilateral to the injected side and ipsilateral turning in resp onse to systemic administration Of DL-methamphetamine. These results s uggest that the dopaminergic innervation exerts a tonic inhibitory act ion on the spontaneous activity of the subthalamic neurons. The loss o f this action would cause muscular rigidity and motor asymmetry.