川芎嗪对犬心脏血流动力学的作用

给麻醉犬静脉滴注川芎嗪1、2及4 mg/kg/min,连续10分钟;动物出现心率加快,心肌收缩力加强,血管扩张。这些作用随剂量的增加而加强。滴注1 mg/kg/min时,心率、LVP及dp/dt max增加,2 mg/kg/min时,心率、LVP、dp/dt max及冠脉血流明显增加。剂量增至4 mg/kg/min时,除上述指标明显增加外,还出现LVEDP、CI,心肌氧耗和脑血流增加,冠状动脉和脑血管阻力及总外周阻力降低。给清醒高血压犬滴注川芎嗪4 mg/kg/min及一次静注20'mg/kg也引起心率加速。心得安(ⅳ1～2 mg/kg)能对抗川芎嗪对麻醉和清醒犬的上述作用,而利血平则不能完全对抗川芎嗪的作用。

EFFECTS OF TETRAMETHYLPYRAZINE ON CARDIAC HAEMODYNAMICS IN DOGS

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.