Wada Y, Satoh K, Taira N
Naunyn Schmiedebergs Arch Pharmacol. 1985 Feb;328(4):382-7. doi: 10.1007/BF00692905.
Bay k 8644, although belonging to dihydropyridines, has been reported to exert effects directionally opposite to those of dihydropyridine calcium channel blockers such as nifedipine. The present experiments were carried out to elucidate whether this is indeed true. All experiments were done on isolated, blood-perfused dog-heart preparations described below, and Bay k 8644 was administered intra-arterially. In sinoatrial (SA) node preparations Bay k 8644 increased sinus rate by about 37% of the basal value at the highest dose (10 micrograms). In atrioventricular (AV) node preparations Bay k 8644 decreased AV conduction time by accelerating AV nodal but not intraventricular conduction. However, the decrease in AV conduction time remained at about 10 ms (about 7.8% of the basal value) even at the highest dose (10 micrograms). In papillary muscle preparations driven at a fixed rate of 120 stimuli/min Bay k 8644 increased the force of contraction by about 100% of the basal value at the highest dose (10 micrograms). In spontaneously beating papillary muscle preparations Bay k 8644 failed to increase the rate of automaticity although it increased the force of contraction. In all preparations Bay k 8644 decreased (coronary) blood flow down to about 20% of the basal value at the highest dose (10 micrograms). The positive chronotropic and dromotropic effects of Bay k 8644 reached respective peaks nearly at the same time as its vasoconstrictor effect, whereas its positive inotropic effect reached a peak after the vasoconstrictor effect had nearly worn off.(ABSTRACT TRUNCATED AT 250 WORDS)
Bay k 8644虽然属于二氢吡啶类，但据报道其作用方向与硝苯地平之类的二氢吡啶类钙通道阻滞剂相反。进行本实验是为了阐明情况是否确实如此。所有实验均在如下所述的离体、血液灌注犬心标本上进行，且Bay k 8644通过动脉内给药。在窦房（SA）结标本中，Bay k 8644在最高剂量（10微克）时使窦性心率增加约为基础值的37%。在房室（AV）结标本中，Bay k 8644通过加速房室结而非心室内传导来缩短房室传导时间。然而，即使在最高剂量（10微克）时，房室传导时间的缩短仍保持在约10毫秒（约为基础值的7.8%）。在以120次刺激/分钟的固定频率驱动的乳头肌标本中，Bay k 8644在最高剂量（10微克）时使收缩力增加约为基础值的100%。在自发搏动的乳头肌标本中，Bay k 8644虽增加了收缩力，但未能提高自律性。在所有标本中，Bay k 8644在最高剂量（10微克）时使（冠状动脉）血流量降至约为基础值的20%。Bay k 8644的正性变时和变传导效应与其血管收缩效应几乎同时达到各自峰值，而其正性变力效应在血管收缩效应几乎消退后才达到峰值。（摘要截选至250词）
