OR discrimination: a new drug discrimination method.

Rats were trained to respond on one of two levers for food (drug lever) after injections of either 0.04 mg/kg fentanyl or 10 mg/kg cocaine HCl, and to respond on the saline lever after saline injections. The acquisition data indicate that this OR discrimination is feasable in the rat, though it developed slowly due to a bias of responding on the drug lever. The generalization data obtained here suggest that the OR discrimination method may establish relations between the cuing properties of drugs which are not apparent with the commonly used drug-saline method of drug discrimination.