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用保持家兔处于闭胸状态记录心外膜心肌单相动作电位(MAP)的技术,研究垂体后叶素(Pt)对MAP的影响及机理。结果表明,Pt可致动物心率减慢、MAP振幅和V_(max)降低、MA时限延长和MAP间期不等以及室性早搏等。用阿托品(1mg/kg iv)或心得安、立其丁(各1mg/kg iv)或同时给予三种受体阻断剂后,再用Pt(2u/kg iv),出现与上述基本一致的电生理改变。结果提示:心肌MAP改变的机理是由于Pt直接作用于全身血管平滑肌使之收缩,外周阻力增加,心室的后负荷增大,心输出量减少和冠状动脉收缩血流阻力增加所致的全心性缺血。
The effect and mechanism of pituitrin (Pt) on MAP were studied by recording the single-phase action potential (MAP) of epicardial myocardium while keeping the rabbit closed. The results showed that Pt could slow down the heart rate, decrease MAP amplitude and V max, prolong the MA duration, vary the MAP interval, and premature ventricular contractions. Substantially consistent with the above, with atropine (1 mg / kg iv) or propranolol, rosetra (1 mg / kg iv each) or with three receptor blockers simultaneously followed by Pt (2 u / kg iv) Electrophysiological changes. The results suggest that the mechanism of MAP changes in myocardium is due to the direct effect of Pt on systemic vascular smooth muscle contraction, increased peripheral resistance, increased ventricular afterload, decreased cardiac output and coronary heart disease caused by increased systolic blood flow resistance Ischemia.