THE EFFECTS OF DOPAMINERGIC AGENTS ON REACTION-TIME IN RHESUS-MONKEYS

Many CNS pathologies, including Parkinson's, Alzheimer's and Huntingto n's diseases, as well as AIDS dementia complex, involve some degree of movement dysfunction. Reaction time (RT) performance has been shown t o be a sensitive measure of motor function for these disorders. Useful models of RT performance exist in a variety of species, but few are p erformed in the same manner as with humans. To facilitate species comp arisons, the present RT task was developed from a human RT task. Dopam inergic drugs were then used to characterize the sensitivity of the mo del to CNS changes and to investigate their effects on RT performance in intact rhesus monkeys. With cumulative dosing, the selective dopami ne receptor antagonists (D-1) SCH 39166 and (D-2) raclopride produced dose-dependent slowing of RT performance. Results following bolus admi nistration of these drugs were consistent with the cumulative dosing p rocedure, although of smaller magnitude and higher variability. Amphet amine had no significant effect on group RT performance with either do sing scheme, but RT performance in individual monkeys was either speed ed or slowed by d-amphetamine. The present results suggest that blocka de of either D-1-like or D-2-like dopamine receptors can slow RT perfo rmance in rhesus monkeys and that this paradigm may be useful to study movement dysfunction in non-human primates.