Time course of chronic haloperidol and clozapine upon operant rate and duration.

Operant response rate and average response duration were recorded for two groups of six rats each responding under a FR 10 schedule of food reinforcement. Using a chronic dosing regime, the effects of haloperidol (0.5 mg/kg) on operant performance were evaluated in one group 2.5, 5.0, 7.5 and 10.0 h after drug treatment. The other group received clozapine (5.0 mg/kg) 1.0, 2.0, 3.0 and 4.0 h before data collection. For both drugs time since injection produced significant effects on both rate and duration: rate increased and duration decreased as a function of time after injection. Haloperidol tended to have a greater lengthening effect upon response duration than did clozapine. In addition, changes in behavior as a function of time after haloperidol injection were observed to approximate previously published pharmacokinetic data for haloperidol administered according to dosing regimens similar to those used here.