The alteration of aversive thresholds after chronic administration of two tranquilizing agents

Abstract

A major tranquilizer, chlorpromazine (0.06, 0.125, 0.25 mg/kg), and a minor tranquilizer, chlordiazepoxide (2.0, 4.0, 8.0, 16.0, 32.0 mg/kg), were administered to squirrel monkeys performing under a titration schedule to ascertain their effects upon aversive thresholds. Both agents reliably raised the aversive threshold to electric shock, but chlorpromazine was more potent in this regard. Chlordiazepoxide was able to augment the aversive threshold to moderate levels only under the middle range (i.e., 8.0, 16.0 mg/kg) of doses tested, while chlorpromazine was able to raise the threshold to maximum levels under the 0.25 mg/kg dosage. These results were interpreted to suggest that chlordiazepoxide may have analgesic properties at moderate doses, while chlorpromazine may raise the aversive threshold by interfering with the execution of the operant response.