[Development of tolerance to the activating action of morphine, fenamin, and alcohol on the positive reinforcement system of rats].

The development of cross tolerance to morphine, amphetamine and alcohol according to their activating effect on the system of positive reinforcement of the brain was shown on the basis of experimental self-stimulation reaction. It is assumed that the common neurophysiological and neurochemical mechanisms, particularly the adrenergic mechanisms of the system of positive reinforcement, lie at the basis of the development of tolerance to the drugs with euphoric type of action.