Interaction of Cocaine and Tyramine on the Isolated Mammalian Heart

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Abstract
Cocaine added to the fluid perfusing the isolated guinea-pig heart antagonised the action of tyramine in reducing the noradrenaline content of the heart. The extent of the antagonism depended on the concentration of cocaine in the perfusion fluid and on the amount of tyramine administered to the heart. Cocaine exerted its antagonistic action in concentrations which had no effect on the release of noradrenaline from the isolated heart, as judged by the absence of change in the noradrenaline content of the heart, and by the absence of a decrease in heart rate. These results may account for the antagonism by cocaine of the sympathomimetic actions of tyramine.