Haloperidol Effects on Morphine Self-Administration: Testing for Pharmacological Modification of the Primary Reinforcement Mechanism

Abstract

Rats were allowed to acquire morphine self-administration behavior and then were extinguished. Following extinction, pre-treatment with saline and various doses of haloperidol were given before a reacquisition test. Reacquisition data indicated that a low dose of haloperidol increased self-administration, while higher doses reduced responding. Data from a second experiment using conditioned reinforcement demonstrated that haloperidol did not block the reinforcing action of morphine. Results are discussed in terms of a need to differentiate between reinforcement antagonism and motor impairment.