The effects of chlorpromazine upon fear-motivated behavior in the squirrel monkey

Four male squirrel monkeys were subjected to a Sidman non discriminated avoidance schedule (R-S, S-S-20 sec) that superimposed 3-min conditioned stimuli (CS)/unavoidable shock pairings upon ongoing avoidance behavior. Three of the four animals demonstrated facilitated avoidance and activity rates during the CS, while one animal demonstrated suppressed avoidance and activityvrates during the CS. Chlorpromazine (.05, .10, .20 mg/kg) reduced overall response rates and augmented shock rates significantly in a dose-related manner. The facilitation ratios computed to reflect the degree of response facilitation for three of the animals during the aversive CS were not significantly altered by drug administration. The one animal which normally suppressed its rate during the CS, however, demonstrated an attenuation of this suppression under all doses of the drug. These results were interpreted to suggest that the degree of behavioral facilitation noted during an aversive CS cannot be used as a sensitive index of the anxiolytic properties of drugs.