Experimental research about the influence of pentazocine and reserpine on morphine addiction

By means of a conveyer belt two types of conditioned reflexes were developed in rats, at two functional levels. When these had become stable, we observed the animals' behaviour during a morphine treatment, until they developed tolerance. Thereafter the treatment with morphine was suddenly discontinued, or morphine was replaced by pentazocine or reserpine. We found that morphine impaired both types of conditioned reflexes and that ni about two weeks drug tolerance appeared. When treatment was discontinued a syndrome of abstinence developed, which exclusively impaired the conditioned reflex of the second order. Pentazocine and reserpine prevent such manifestation of the abstinence syndrome. Moreover, reserpine suppresses the tolerance to morphine. Concerning these results we suppose that opioid receptors type mu are involved in behavioural trouble produced by morphine, while opioid receptors type k are involved in the abstinence syndrome. Certain adrenergic mechanisms operate both in the development of tolerance and in behavioural modifications caused by the syndrome of abstinence.