Extended schedule transfer of ethanol discrimination.

Stimulus control was established in rats with ethanol (600 mg/kg) and saline by employing a two-lever response choice task and an FR10 schedule of food reinforcement. Subjects were then tested with an extended schedule procedure in which lever selection and its perseverance were measured under the training conditions and after the administration of pentobarbital at doses of 2 to 12 mg/kg. With decreasing doses of pentobarbital, drug-lever selection was observed to decline. The dose at which initial lever selection was evenly distributed between the two levers (ED50) was determined to be 4 mg/kg. However, at this dose the perseverance on the ethanol-appropriate lever was not significantly different than that observed after the training dose of ethanol. In addition, the perseverance of saline-lever selection produced by saline was observed to be greater than that produced by the training dose of ethanol on the ethanol-lever. The advantages inherent in employing the extended schedule performance procedure in transfer experiments are discussed.