ACTION OF TETRAMETHYLPYRAZINE ON CARDIOVASCULAR SYSTEM IN THE ANESTHETIZED DOG (PRELIMINARY STUDY)

Tetramethylpyrazine (TMPZ) has been shown to be one of the active principles of the Chinese medicinal plant "Chuan Qong", Ligusticum Wallichii Franch.TMPZ (4, 8 or 16 mg/kg) given intravenously to anesthetized dogs transiently decreased the blood pressure and markedly increased the heart rate and maximal rate of the left ventricular pressure. These cardiovascular effects of TMPZ seemed to be dosedependent. Prior administration of propranolol (2 mg/kg, I. V.) abolished the effect of TMPZ on the heart, leaving the depressor effect of TMPZ unchanged. Reserpinization of the dog affected the cardiovascular actions of TMPZ in a way similar to propranolol. The cardiovascular responses to TMPZ still persisted after cervical vagotomy. The injection of TMPZ at a dose of 0.4～2 mg/kg into the vertebral artery induced no significant hemodynamic response.These results indicate that in the anesthetized dog TMPZ exhibited positive inotropic and chronotropic effects on the heart mediated by sympatho-adrenergic mechanism. In addition, TMPZ seemed to have some direct dilating action on the peripheral bloodvessels.