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A-V and intraventricular conduction disturbances induced by 3 different salts of ajmaline: N-propyl ajmaline bitartrate (NPAB), hydrochloride (CHA) and mono chloro-acetate (MCAA), were studied by recording endocavitary His bundle activity in pentobarbital anesthetized dogs. Cumulative dose-response curves were obtained with 3 doses of each compound. The results demonstrate that: a) NPAB exerts a significant depressor effect (9 to 10 times more potent than CHA) on the following three conduction times: auriculo-Hisian, His-Pinkinje and Purkinje-ventricular; b) on His-Purkinje and intra ventricular conduction, MCAA exerts a weaker depressor effect than that of Nab. The lack of parallelism of dose-response curves prevents further comparative quantification; c) on atrio-hisian conduction, MCAA presents a delayed dose-related depressor effect suggesting the presence of an active metabolite. It is concluded that among ajmaline derivatives studied, Nab appears to be the most depressor on A-V and intraventricular conduction in the pentobarbital anesthetized dog.

Two salicylamides, thiapride and sultopride, were found to provoke a dose-related depressor effect in the anesthetized dog. This effect was qualitatively similar to that of procaïnamide and metoclopramide. The hypotensive and negative inotropic effects were not related to the parasympathic system. In fact these compounds are weak autonomic antagonists. They do not exert any anticholinesterase activity. Intra-arterial administration provoked vasodilation.

The antiarrhythmic effect of Metoclopramide and its analogs, sultopride and thiapride, were studied. In the dog arrhythmias were induced by epinephrine, ouabain and coronary artery ligation. In the guinea-pig the effect of each compound was determined on the ouabain-induced arrhythmias as well as on the refractoriness of the electrically stimulated isolated atria. In the dog sultropide and thiapride were less active than metoclopramide. However, metoclopramide and thiapride depressed auriculo-ventricular conduction. None of these agents exerted a protective antiarrhythmic effect in the guinea-pig. Metoclopramide increased the refractoriness while sultropide and thiapride were almost inactive. Unlike metoclopramide, the two analogs have no local anesthetic activity.