ACTIVATION OF SUBTHALAMIC NEURONS PRODUCES NMDA RECEPTOR-MEDIATED DENDRITIC DOPAMINE RELEASE IN SUBSTANTIA-NIGRA PARS RETICULATA - A MICRODIALYSIS STUDY IN THE RAT

Here we have studied whether the activation of the subthalamic neurons induces the release of dopamine (DA) from dopaminergic dendrites in t he pars reticulata of the substantia nigra. Subthalamic neurons were a ctivated by carbachol microinjected into the subthalamic nucleus. A mi crodialysis probe was implanted in the medial aspect of the pars retic ulata to collect samples of the perfusate. Carbachol (1 mu g/0.25 mu l saline) enhanced (58 +/- 8% over basal values) nigral DA release. The enhancement was fully blocked by the NMDA antagonist AP5 added to the microdialysis medium perfusing the pars reticulata. Perfusion of the pars reticulata with NMDA also increased (125 +/- 25% over basal) nigr al DA release. Again, AP5 reversed the effect. These results suggest t hat activation of the glutamatergic subthalamonigral pathway enhances dendritic DA release by activating NMDA receptors present on dopaminer gic dendrites.