Self-administration of cocaine on a progressive ratio schedule in rats: dose-response relationship and effect of haloperidol pretreatment.

Intravenous cocaine self-administration behavior in rats was investigated using a progressive ratio (PR) schedule of reinforcement. The first response on the lever each day produced a drug infusion, whereupon the requirements of the schedule escalated with each reinforcement until the behavior extinguished. The final ratio completed each day was found to be relatively stable, sensitive to changes in dose, and drastically reduced by pretreatment with haloperidol (0.05 mg/kg). We conclude that self-administration behavior of rats reinforced on a progressive ratio schedule can provide useful information about changes in the reinforcing efficacy of specific drugs.