Li Q, Qian J Q
Department of Pharmacology, Tongji Medical University, Hankou, China.
Zhongguo Yao Li Xue Bao. 1990 Jan;11(1):21-5.
In rat working hearts, alpha 1-adrenoceptor agonist phenylephrine increased LVP, +/- dP/dtmax, ABF and HR in the presence of propranolol. But alpha 2-adrenoceptor agonist B-HT 920 was ineffective. The changes induced by phenylephrine were antagonized by prazosin. In normotensive pithed rats, iv methoxamine dose-dependently increased LVP, +/- dP/dtmax, LVEDP, SAP and DAP. The changes in haemodynamics elicited by iv methoxamine were also antagonized by pretreatment with prazosin, and were attenuated by nifedipine (1 mg/kg, ia). In these two experiments, the increase in HR developed more slowly. The results suggest that postjunctional alpha 1-adrenoceptors, which exist in rat myocardium, produce a positive inotropic effect, which is possibly dependent on influx of extracellular calcium. Postjunctional alpha 2-adrenoceptors-mediated effects were not found in rat myocardium in our functional studies.
在大鼠工作心脏中，在普萘洛尔存在的情况下，α1 -肾上腺素能受体激动剂去氧肾上腺素可增加左心室压力（LVP）、±最大dp/dt、主动脉血流量（ABF）和心率（HR）。但α2 -肾上腺素能受体激动剂B-HT 920无效。去氧肾上腺素引起的变化可被哌唑嗪拮抗。在正常血压的脊髓横断大鼠中，静脉注射甲氧明可剂量依赖性地增加LVP、±最大dp/dt、左心室舒张末期压力（LVEDP）、收缩期动脉压（SAP）和舒张压（DAP）。静脉注射甲氧明引起的血流动力学变化也可被哌唑嗪预处理拮抗，且可被硝苯地平（1毫克/千克，腹腔注射）减弱。在这两个实验中，心率的增加发展较为缓慢。结果表明，大鼠心肌中存在的节后α1 -肾上腺素能受体产生正性肌力作用，这可能依赖于细胞外钙的内流。在我们的功能研究中，未在大鼠心肌中发现节后α2 -肾上腺素能受体介导的效应。
