Effects of subthalamic nucleus lesions and stimulation upon glutamate levels in the dopamine-depleted rat striatum.

It is not known how neurosurgical interventions benefit patients with Parkinson's disease. We compared the effects of electrical stimulation and electrolytic lesions of the subthalamic nucleus upon striatal extracellular glutamate levels in awake rats, either intact or which had undergone unilateral 6-hydroxydopamine lesions. Two hours of subthalamic nucleus stimulation had no effect in either group. Subthalamic nucleus lesions of intact animals increased striatal glutamate levels. Subthalamic nucleus lesions of 6-hydroxydopamine-lesioned rats decreased striatal glutamate levels. As dopamine depletion alone increased striatal glutamate, subthalamic nucleus lesioning decreased levels to normal. Thus, subthalamic nucleus lesions and short-term stimulation have different effects upon striatal glutamate. The effects of lesions differed depending upon the presence of dopamine. These results suggest that short-term electrical stimulation does not result in a direct inhibitory effect upon the subthalamic nucleus.