Clozapine effects on responding maintained under shock presentation and shock termination schedules

Clozapine, a novel antipsychotic, was studied in different squirrel monkeys responding under a 3-min fixed-interval schedule of stimulus-shock termination and a multiple 5-min fixed-interval schedule of shock presentation, 5-min fixed-interval schedule of stimulus-shock termination. Some doses (0.1-1.0 mg/kg IM) of clozapine increased responding under each fixed-interval schedule, whereas higher doses (3.0 and 5.6 mg/kg IM) usually decreased responding under each schedule. Lower response rates maintained under the stimulus-shock termination schedule were increased relatively more by clozapine than were higher rates of responding maintained under the fixed-interval schedule of shock-presentation. The present results illustrate that the effects of clozapine on schedule-controlled behaviors of squirrel monkeys differ from those of other antipsychotics.