Effect of opiate receptor agonists and antagonists on the resistance of animals to hypoxic hypoxia

: The effects of morphine, a series of synthetic enkephalin analogs and antagonists of narcotic analgesics on the animals' survival rate under hypoxic hypoxia were studied in experiments on mice, rabbits, and cats. It was shown that the agonists of mu-opiate receptors, morphine, FK 33-824 (Tyr-D-Ala-Gly-MePhe-Met-(O)-ol, Tyr-D-Ala-Gly-Phe-(NO2)-NH2 and Tyr-D-Ala-Gly-MePhe-Gly-ol increase the survival rate in a hermetic chamber and that this effect is arrested by naloxone, nalorphine, and TRH. Tyr-D-Ala-Gly-D-Leu, an agonist of delta-opiate receptors has no antihypoxic properties. The data obtained point to the involvement of opiate receptors (at least of those of the mu-type) in realization of the reactions that increase the resistance to hypoxia. Bicuculline was shown to be able to remove the antihypoxic effect of the agonists of opiate receptors, suggesting the GABAergic modulation of this effect.