An investigation of nalorphine and perphenazine as negative reinforcers in an escape paradigm.

Rhesus monkeys were trained to self-administer morphine intravenously at dose levels sufficient to develop physical dependence. The monkeys were then trained to press a lever to escape a continuous infusion of the morphine antagonist, nalorphine. When saline was substituted for the nalorphine, escape responding extinguished. After morphine self-administration was eliminated, responding to escape from nalorphine was maintained in the postdependent monkeys, showing no difference from escape responding during morphine dependence. Finally, perphenazine was substituted for the nalorphine and the monkeys reliably escaped continuous infusions of this phenothiazine. The escape procedure appears useful for analyzing the aversive properties of drugs.