CARDIAC RESPONSE TO POSTERIOR PITUITARY EXTRACT AS AFFECTED BY SODIUM PHENOBARBITAL

¹ Department of Pharmacology, McGill University, Montreal, Canada

1. It is shown that postlobin-V in large doses (1.5 units per kgm.) leads to ventricular fibrillation and death in dogs anesthetized with sodium phenobarbital.

2. This effect may be prevented by the previous administration of ephedrine, adrenaline and papaverine.

3. The data suggest that the degree of coronary constriction produced by postlobin-V in the phenobarbitalized heart is relatively greater than in the normal or chloretonized heart.

4. Using the heart-lung preparation it may also be shown that sodium phenobarbital per se depresses the total heart output relatively earlier and more markedly than the coronary output.

5. It is concluded then that the increased deleterious cardiac effects (ventricular fibrillation) induced by pituitary extract in the phenobarbitalized heart, are due to both the increased coronary constrictor action of the extract, as well as to some depressant myocardial effect of sodium phenobarbital whereby the normal ventricular conduction is disturbed.

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