Wu X, Huang W Q, Zhang Q Q, Yu Z M
Department of Physiology, Nantong Medical College, P.R. China.
Methods Find Exp Clin Pharmacol. 1994 Oct;16(8):583-7.
The effects of histamine on action potentials (APs) and on early afterdepolarizations (EADs) were studied with standard microelectrode and computer in guinea pig papillary muscles. Experiments offer evidence that histamine (6.0 mumol/l) results in a significant diminution in action potential duration at 50% repolarization (APD50) and 90% repolarization (APD90) (data taken from no abnormal automaticity and oscillatory potential cells, 10 out of 19 preparations). Particularly, histamine can induce EADs (about 58%), oscillatory potentials and triggered activity. EADs frequently occur at low stimulation rates of 0.2-1.0 Hz and with prolongation of the action potential duration. EAD-induced triggered activity may exhibit fast spontaneous APs. Cimetidine (10 mumol/l, n = 6), an H2-receptor antagonist, antagonizes the effects of histamine. In the presence of cimetidine no EADs are observed by perfusing histamine. An H1-receptor antagonist, chlorpheniramine (10 mumol/l, n = 9), has no effect on the alterations of APs induced by histamine in ventricular myocardium. The results suggest that the mechanisms of histamine-induced shortness of AP duration, EADs and triggered activity may be related to the H2 receptor-mediated enhancement of the slow inward calcium current.
采用标准微电极和计算机技术，在豚鼠乳头肌上研究了组胺对动作电位（APs）和早期后去极化（EADs）的影响。实验提供的证据表明，组胺（6.0 μmol/L）可导致复极化50%时的动作电位时程（APD50）和复极化90%时的动作电位时程（APD90）显著缩短（数据取自无异常自律性和振荡电位的细胞，19个标本中有10个）。特别是，组胺可诱发EADs（约58%）、振荡电位和触发活动。EADs常出现在0.2 - 1.0 Hz的低刺激频率下，且动作电位时程延长。EADs诱发的触发活动可能表现为快速的自发动作电位。H2受体拮抗剂西咪替丁（10 μmol/L，n = 6）可拮抗组胺的作用。在存在西咪替丁的情况下，灌注组胺时未观察到EADs。H1受体拮抗剂氯苯那敏（10 μmol/L，n = 9）对组胺诱导的心室肌动作电位改变无影响。结果表明，组胺诱导的动作电位时程缩短、EADs和触发活动的机制可能与H2受体介导的慢内向钙电流增强有关。
