Further experimental evidence for a smooth muscle depressant effect of ketamine.

The effect of ketamine on the rat uterus in oestrus and the guinea pig ileum was investigated to determine whether the drug has smooth muscle relaxant properties dependent upon beta adrenergic stimulation or an anticholinergic effect. The results with the rat uterus clearly showed that relaxation was not due to action at the beta adrenergic receptors. On this muscle preparation ketamine depressed carbachol-induced contractions. This anticholinergic action of ketamine was investigated on the guinea pig ileum. Dose response curves were obtained for acetylcholine, histamine and barium chloride in the presence of ketamine. The results showed that ketamine effectively reduced contractions elicited by the three agonists. It is concluded that ketamine is not a beta receptor agonist and it is unlikely that the drug is a specific cholinergic antagonist.