Effects of an extract of khat (Catha edulis) on the toad heart

The effects of acute and chronic administration of an extract of Catha edulis on the heart of the toad were investigated. ECG and ventricular action potential were recorded simultaneously from the surface of the heart of spinal pithed toads before and after administration of different doses of khat extract. Acute treatment resulted in a dose-dependent chronotropic effect and an increase in the amplitude of ventricular action potential. Chronic treatment on the other hand resulted in a negative chronotropic effect and a reduction in the amplitude of ventricular action potential. The observed responses are explained on the basis of the catecholamine releasing effect of components of khat extract.