Metabotropic glutamate receptor 4 in the basal ganglia of parkinsonian monkeys: Ultrastructural localization and electrophysiological effects of activation in the striatopallidal complex

► Basal ganglia mGluR4 in primates is concentrated in GP, SNr and striatum. ► mGluR4 is found in glutamatergic and GABAergic terminals in the GPe and striatum. ► Local group III mGluRs activation increases pallidal activity in monkeys. ► Group III mGluRs activation increases and decreases striatal activity in monkeys. ► Group III mGluRs activation increases firing irregularity in the monkey striatum.