[Attenuation of the action of morphine in rats immunized with a conjugated morphine-protein antigen].

The effect of immunization of rats with the conjugated antigen morphine-bovine serum albumin synthetized by the authors on the analgetic activity of morphine hydrochloride has been investigated. Morphine binding antibodies were shown to appear in the blood of rats during immunization. The spleen demonstrated mononuclear cells also capable of morphine binding. It has been established that immunization of rats with the above synthetic antigen makes them tolerate the pharmacological effects of the narcotic. Morphine at a dose of 5 mg/kg is not capable of inducing an inherent increase in the threshold of pain sensitivity in immunized rats. Immunization also slightly diminishes the morphine effect at a dose of 20 mg/kg on the EEC. Prolonged daily administration of morphine does not remove morphine tolerance due to immunization.