REBOUND RESPONDING FOLLOWING A SINGLE-DOSE OF DRUG USING AN AMPHETAMINE-VEHICLE-HALOPERIDOL DRUG DISCRIMINATION

The purpose of this research was to characterize drug-induced rebound cue states using a three-choice, agonist-vehicle-antagonist drug-discr imination procedure. Rats were trained to discriminate among 0.50 mg/k g amphetamine (AM), distilled water (DW), and 0.03 mg/kg haloperidol ( HA) in a three-lever drug discrimination task. Time-dependent changes in cue state were assessed following single doses of AM (5 and 10 mg/k g), HA (1 mg/kg), and cocaine (30 and 40 mg/kg). Consistent with expec tations derived from the results of a study that used a two-lever AM-H A discrimination task, single doses of AM produced rebound responding on the HA-appropriate lever that was dose-dependent and peaked at 24 h following administration. In addition, cocaine substituted for AM at 0.5-2 h post-injection and then produced HA-like rebound responding th at peaked at 24-36 h post-administration. Contrary to expectations, ho wever, rebound AM-like responding did not occur following HA administr ation. Perhaps two- and three-choice discrimination tasks differ in th eir ability to characterize qualitative aspects of the post-haloperido l cue state. Knowledge of the time course of drug-induced adaptive pro cesses, measured as withdrawal in the present research, is necessary f or a complete description of a drug's effects and is important in unde rstanding the effects of repeated drug administration.