Effects of cannabinoids on the perfused rat heart.

In the isolated perfused rat heart cardiac rate and contractility are directly affected by four naturally occurring cannabis constituents, delta9-tetrahydrocannabinol, delta8-tetrahydrocannabinol, cannabinol and cannabidiol. All the drugs depressed myocardial contractility. Their effect on rate, however, was not uniform: delta8-Tetrahydrocannabinol produced cardiac arrhythmias but no other consistent change; both delta9-tetrahydrocannabinol and cannabinol caused tachycardia; but cannabidiol produced bradycardia, arrhythmias and asystole. In addition, as a consequent of the dispostion of the cannabinoids to accumulate in the isolated heart, high tissue concentrations appeared in conjunction with the direct cardiac effects.