Effects of corticotropin releasing factor, desipramine and haloperidol on a DRL schedule of reinforcement.

Rats were trained on a schedule of differential-reinforcement-of-low-rate (DRL) which has been proposed to be differentially sensitive to antidepressant drugs. Desipramine and haloperidol decreased response rate and increased reinforcement rate. CRF decreased response rate and failed to change reinforcement rate. Amphetamine produced the opposite pattern of increased response rate and decreased reinforcement rate. These results question the specificity of the DRL task as a screen for antidepressants and suggest that drugs that moderately lower response rate may produce a behavioral profile on this task similar to that of tricyclic antidepressants.