PHARMACOLOGICAL STUDIES OF EXTRACTS OF TUSSILAGO FARFARA L. (Ⅱ) EFFECTS ON THE CARDIAO-VASCULAR SYSTEM

Intravenous injection of the alcoholic extracts or decoctions of Tussilago farfara L. to cats anaethetized with pentobarbital sodium induced a primary transitory depressor effect which was followed by a more rapid acute rise in mean blood pressure and finally a sustained pressor response for several minutes. Usually the primary depressor response was absent when ether extract was used. The pressor peak was obtained quickly in rats, cats, dogs and rabbits. No tachyphylaxis was observed. The pressor response was associated with increases of heart rate and respiratory stimulation. The nictitating membranes of cats were contracted parallel to the elevation of blood pressure.The pressor response was also obtained from the route of arteria vertebralis, cisterna cerebello-medullaris and in decerebrated cats, but weakened in spinal preparations. It was partially inhibited by pretreatment with ganglionic agents and nearly disappeared after chlorpromazine injection. It was not influenced by adrenalectomy or sympathoplegic drugs nor by pre-administration of reserpine. The ether extract was also effective intraarterially. The blood vessels were constricted as tested by means of Frlich and Laewen-Trendelenburg's methods and the plethysmograph of the kidney. From these experiments, it appears that the mechanism of action of Tussilago on blood pressure may be due to stimulation of the vasomotor center of medulla, and the vascular α-receptor and constriction of the peripheral blood vessels