DOPAMINERGIC &GABAERGIC ACTIONS ON PALLIDAL DISCHARGE

Our current objectives are to determine the actions of dopamine via D1 and D2 receptors on tonic and phasic discharge of neurons in external and internal pallidal segments, and to study the effects of striatal GABA on striatal output neurons. Pharmacological agents have been applied to the striatum through implanted PAN-PVC tubing in three monkeys. In all, the technique developed by Dr. Dubach has resulted in accurate placement of the tubing along a curved longitudinal trajectory in the lateral portion of the putamen. We have applied the D1-selective antagonist SCH23390 and the D2-selective antagonist raclopide successfully while monitoring behavior and recording from pallidal neurons. In high concentrations similar to those injected by others into the cortex, both agents interrupted behavior, and SCH23390 caused drowsiness. Even at concentrations reduced by 10- to 100-fold, the animal stopped working, but only after a longer drug perfusion and with a shorter wash out time to behavioral recovery. The behavioral data showed that, even when the intervals between successful trials were very long, the reaction time and movement time for successful trials was not significantly longer than the times before or after drug application. This suggests that drug administration alters attention, more than processes directly related to motor output. FUNDING NIH grants RR00166 and NS15017. Anderson, M.E., Dubach, M., Ruffo, M., Eaton, R., and Buford, J.A. Effects on motor behavior of dopamine antagonists applied locally in the putamen of awake monkeys. Soc. Neurosci. Abstr. 24:1650, 1998.