Neurotransmitter and neuropeptide mechanisms responsible for the development of a withdrawal syndrome in morphine-dependent animals

The neurotransmitter and neuropeptide mechanisms responsible for the development of the morphine drug dependence and a withdrawal syndrome (WS) were studied in rats. Physical dependence and WS were found to develop against the background of restricted responsiveness of the adrenergic and dopaminergic systems. At the same time, the activity of the serotonin-, GABA-, vasopressin-, and oxytocinergic systems is suppressed at the WS. Agonists of opiate receptors, butorphanol and loperamid, were shown to improve the physical state of the animals with a WS. Similar action was found to be exerted by activators of the adrenergic system (ephedrine, phenylephrine), dopaminergic system (levoDOPA, apomorphine), and serotonergic system (tryptophan), as well as by neuropeptides, vasopressin and oxytocin.