Abstract: The effects of tetramethylpyrazine (TM) on femoral, cerebral and coronary blood flow and cardiac function were examined in 18 anesthetized dogs. Intravenous infusion of TM (1, 2, 4 mg/kg/min for 10 min) produced a dose-dependent positive inotropic, chronotropic and vasodilatory effect. The HR, LVP and LV dp/dt max were increased by infusion of TM 1 or 2mg/kg/min. During administration of TM 4 mg/kg/min, these effects were found to be more marked. In addition, a significant increase in cardioindex (CI) and left ventricular end diastolic pressure (LVEDP) and a decrease of total peripheral resistence (TPR) were observed.Blood flow was measured by means of electromagnetic flow meter. Administration of TM 4 mg/kg/min induced an augmentation of the coronary and cerebral blood flow and reduction of their vascular resistence, while the myocardial O₂ consumption was elevated. The cardiotonic and vasodilatory effects induced by TM in anesthetized dogs could be antagonized by iv propranolol (1 mg/kg), but not abolished by im reserpine 0.2～0.3mg/kg 24 hours before TM administration.In one spontaneous and four renal hypertensive dogs, TM (infusion of 4mg/kg/min or a single iv dose of 20mg/kg) also elicited a positive chronotropic effect. This effect disappeared after iv injection of 2mg/kg propranolol. It appears that the cardiohaemodynamic effects elicited by TM is mediated through β-Adrenoreceptor activation.