[Morphine antibodies in the mechanisms of morphine resistance, morphine tolerance and of the action of an antagonist].

It was found that the absence of the analgesic effect of morphine, as determined by the tail-flick test, in morphine-resistant and morphine-tolerant rats, as well as in naloxane blockade of morphine analgesia in morphine-sensitive rats was attended with a four- to eight-fold increase in morphine antibodies in the plasma, as determined by the ELISA method. It is suggested that a pharmacokinetic factor mediated through immune reactions of morphine antibodies formation is one of the mechanisms of such conditions.