The action of strophanthus on the chloralized heart.

Abstract

In a recent paper 1 I was trying to show—for the cold blooded heart—that in chloral hydrate, if applied in appropriate concentrations, we possess a substance which paralyzes the nervous elements of the heart in precedence to the muscular ones. It was suggested there that we might take advantage of this functional interval (elapsing between the elimination of the nervous elements and the paralysis of the sinus: the end stage of chloral action) in order to analyze the point of attack of certain pharmacological agents. The reactions of the digitalis group were tested first, for, although it is generally known that digitalis action is primarily myotropic, there remains a possibility of neurotropic action, particularly concerning chronotropic and dromotropic activities. The experiments have been carried out on the perfused heart of terrapin (Engelmann's method.) The chloral hydrate concentrations used were 0.01-0.025 per cent. With these concentrations, the functional “denervation level” was reached in about 15-35 minutes. 1 The action, with changes in conductivity and latent period as criteria, is reversible, if Ringer's solution is reapplied before the denervation level of these functions is reached; in later stages chloral hydrate creates irreversible conditions. The perfusion in the interval was therefore conducted with the test drug alone. For this strophanthus was used, in concentrations of from 0.1-0.02 per cent, under pressures of 5-10 mm. Hg., at a perfusion rate of 3-5 cc. per min. Optical auricular and ventricular myograms were taken simultaneously with electrograms. Perfusion with chloral hydrate alone and with strophanthus without previous action of chloral served as controls.

The rate decreased both with and without chloral hydrate, after short transitory acceleration, and the heart stopped always in systole. The auricle was the ultimum moriens.