Effect of ethanol, pentobarbital and morphine on the toxicity of hemicholinium-3 and d-tubocurarine in mice.

Pretreatment of mice with either ethanol, pentobarbital or morphine protected against the lethal effects of hemicholinium-3 (HC-3) but not curare. The protective action of these compounds was not due to an induced release of corticosteroids in vivo since administration of prednisolone did not protect against HC-3 toxicity. The protective action of morphine was reversed by Nalline hydrochloride. The results suggest that the site of the protective action of ethanol, pentobarbital and morphine and the site of action of the lethal respiratory depression by HC-3 are central in origin.