AMPHETAMINE, COCAINE, AND DIZOCILPINE ENHANCE PERFORMANCE ON A LEVER-RELEASE, CONDITIONED AVOIDANCE-RESPONSE TASK IN RATS

A lever-release version of the conditioned avoidance response (CAR) ta sk was used to assess the behavioral effects of several psychomotor st imulants in rats. The indirect dopamine agonists, d-amphetamine (0.1 a nd 0.25 mg/kg) and cocaine (7.5 and 15 mg/kg), enhanced performance on this task. Both drugs increased percent avoidance responses and decre ased avoidance latency. A higher dose of amphetamine (0.5 mg/kg) also decreased avoidance latency but failed to improve percent avoidance. S imilar effects were seen at low (0.01 and 0.025 mg/kg) and high (0.05 mg/kg) doses of dizocilpine (MK-801), a stimulant that acts as a nonco mpetitive antagonist of N-methyl-d-aspartate (NMDA) glutamate receptor s. When combined with haloperidol (0.1 mg/kg), a dopamine antagonist, amphetamine (0.25 mg/kg) and dizocilpine (0.025 mg/kg) had differentia l effects on the lever-release CAR task. Thus, amphetamine-haloperidol was significantly better than haloperidol alone on percent avoidance but not on avoidance latency, whereas dizocilpine-haloperidol had the opposite effect: significantly better than haloperidol alone on avoida nce latency but not on percent avoidance. Taken together, these result s provide further support for dopaminergic mechanisms in CAR performan ce but suggest an opposing glutamatergic influence.