Effects of tricyclic compounds and other drugs having a membrane stabilizing action on analgesia, tolerance to and dependence on morphine.

Several drugs affecting nerve cell excitability, by opposing ion movements in membranes, were tested in mice rendered tolerant to or dependent on morphine. The purpose of the study was to investigate whether these drugs share the ability to attenuate morphine tolerance and dependence exhibited by tricyclic antidepressants. Tolerance to morphine was decreased by the administration of imipramine, doxepin, promethazine, propranolol, lidocaine and quinidine. Chlorpromazine and carbamazepine were ineffective. The intensity of the abstinence syndrome provoked by naloxone was decreased by chlorpromazine, imipramine, doxepin, lidocaine, quinidine and propranolol. Diphenyl. hydantion and carbamazepine had no effect. The results are discussed in relation with the blockade of ion conductance and their interference with the release of neurotransmitters produced by the drugs assayed.