Xue G H, Wang Z Y, Liao D Z, Pan J Y, Zhan C Y
Department of Physiology, Sun Yat-Sen University of Medical Sciences.
Sheng Li Xue Bao. 1990 Aug;42(4):323-30.
The effects of morphine at different concentrations on myocardial action potential were studied in isolated right ventricular papillary muscles of the guinea pig. It was observed that morphine at low concentrations (0.2-1.6 mumol/L) shortened the action potential duration (ADP) and effective refractory period (ERP) in a concentration dependent manner. These effects could be abolished by naloxone (1 mumol/L), phentolamine, tetraethylammonium (TEA) and cesium chloride (Cs+), but not by verapamil. On the other hand, morphine at high concentrations (15-120 mumol/L) prolonged ADP and ERP in a concentration dependent manner. The effects were unaffected by low dose of naloxone (1.2 mumol/L) but were abolished by high dose of naloxone (10 mumol/L), phentolamine, TEA, Cs+ and verapamil. These results suggest that morphine at low and high concentrations might stimulate different subtypes of opioid receptors. The effects of morphine in low concentrations are associated with the activation of potassium channel, whereas the effects of morphine at high concentrations are associated with the activation of potassium channel, calcium channel or calcium activated potassium channel. The action of opioid receptor was closely related to alpha adrenoreceptors.
在豚鼠离体右心室乳头肌上研究了不同浓度吗啡对心肌动作电位的影响。结果发现，低浓度（0.2 - 1.6 μmol/L）吗啡能以浓度依赖的方式缩短动作电位时程（ADP）和有效不应期（ERP）。这些效应可被纳洛酮（1 μmol/L）、酚妥拉明、四乙铵（TEA）和氯化铯（Cs⁺）消除，但维拉帕米不能。另一方面，高浓度（15 - 120 μmol/L）吗啡能以浓度依赖的方式延长ADP和ERP。低剂量纳洛酮（1.2 μmol/L）对这些效应无影响，但高剂量纳洛酮（10 μmol/L）、酚妥拉明、TEA、Cs⁺和维拉帕米可消除这些效应。这些结果提示，低浓度和高浓度吗啡可能刺激不同亚型的阿片受体。低浓度吗啡的效应与钾通道激活有关，而高浓度吗啡的效应与钾通道、钙通道或钙激活钾通道的激活有关。阿片受体的作用与α肾上腺素能受体密切相关。
