SELECTIVE D(1)-DOPAMINE AND D(2)-DOPAMINE RECEPTOR ANTAGONISTS PRODUCED DIFFERENTIAL-EFFECTS ON REACTION-TIME IN THE RAT

The purpose of this investigation was to determine whether selectively blocking D1 and D2 dopamine receptors produces a differential effect on the characteristics (speed and success) of the reaction time respon se in rats. Animals were shaped to release a lever in response to an a uditory/visual stimulus to avoid mild foot shock. The selective D1 ant agonist SCH 23390 (0, 70, and 100 mug/kg, IP) and the selective D2 ant agonists spiperone (0, 1, and 10 mug/kg, IP) and haloperidol (0, 10, a nd 100 mug/kg, IP) were studied for their effects on successful avoida nce and response latency. SCH 23390 impaired successful avoidance and increased response latencies in a dose-dependent manner. Spiperone and haloperidol also produced dose-related decreases in successful avoida nce. In contrast to the dose-related increase in response latencies pr oduced by SCH 23990, 1 mug/kg spiperone and 10 mug/kg haloperidol sign ificantly decreased the latencies of successful responses. Spiperone ( 10 mug/kg) had little effect on response latencies, while 100 mug/kg h aloperidol increased them. The results of these experiments demonstrat e that reaction time is differentially affected by selective dopamine receptor blockade and that the speed and success of reaction time resp onses can be independently modulated by D1 vs. D2 receptor activity.