Inversion of the coronary dilator effect of some drugs by ergotamine tartrate

Abstract

Using the bubble-passage method, through a system for measuring coronary flux, as described in Figure 1, we have made a study, in dogs anesthetized with the mixture of chloralose and uretane, as well as being subjected to artificial respiration and carotid-coronary connection by means of the system proposed, of the effect of ergotamine tartrate on the coronary flux, and of the influence of this alkaloid on the action of certain coronary vasodilators.

Although we are told, in the bibliography consulted, that er­ gotamine produces coronary vasoconstriction, we have seen that this effect is preceded by an increase in the coronary flux, and we attribute this double action to the distinct degree of musculotropic activity possessed by this alkalvid; thus, in a firet phase, this musculotropic action is maximum, showing itself in an increase in the arterial pressure which, in the last instance, is the element capable of overcoming he resistance offered by the coronary bed (?) and of increasing the amount of blood which passes through the vascular-cardiac system. However, when the arterial pressure returns to its norn^l state thorough the action of compensating factors and the decrease in the activity of the ergotamine, the coronary spasm predominates and tberefore the flux decreases.

Apart from this, we have observed the inversion, due to ergo­ tamine tartrate, of the coronary-dilator effect of papaverine, theophiline-ethylenoidiamine and persantine.

We have drawn up a schedule which summarizes the action of these coronary vasodilators (before and after ergotamine tartra­te) on arterial pressure, coronary flux, intensity and duration, as also that of ergotamine tartrate.