Braveny P, Juggi J S, Mohan S S
Can J Cardiol. 1985 Sep-Oct;1(5):310-7.
The negative inotropic effect of nifedipine (0.1-2.5 mg/l) was studied on isolated atria at different temperatures (36 degrees, 29 degrees, 22 degrees C) and frequencies of stimulation (20, 60, 180/min). The effect on peak force and dF/dt increased with dose, frequency and cooling from 36 degrees to 29 degrees. Rate of contraction was affected slightly more than rate of relaxation. The effect on time to peak was small, dose and frequency independent but potentiated by lowering the temperature. An analysis of mechanical transients showed that at 22 degrees C and 180/min stimulation the effect of nifedipine gradually diminished and only slowly reappeared upon transition to 20/min stimulation. In spontaneously beating perfused hearts the effects of nifedipine (0.5 mg/l) in general did not differ significantly at 36 degrees and 23 degrees C. The heart rate was reduced and atrioventricular conduction prolonged. At constant heart rate, nifedipine considerably depressed contractions, shortened the action potential duration and reduced the height of plateau. These effects of nifedipine are similar to those of verapamil in other animal species and the results support the idea that calcium antagonists might have secondary intracellular effects apart from direct consequences of slow current inhibition.
研究了硝苯地平（0.1 - 2.5毫克/升）在不同温度（36℃、29℃、22℃）和刺激频率（20、60、180次/分钟）下对离体心房的负性肌力作用。对峰值力和dF/dt的作用随剂量、频率以及从36℃降至29℃的降温而增强。收缩速率受到的影响略大于舒张速率。对达到峰值时间的影响较小，与剂量和频率无关，但随温度降低而增强。对机械性瞬变的分析表明，在22℃和180次/分钟刺激下，硝苯地平的作用逐渐减弱，而在转变为20次/分钟刺激时仅缓慢重新出现。在自发搏动的灌注心脏中，硝苯地平（0.5毫克/升）在36℃和23℃时的作用总体上无显著差异。心率降低，房室传导延长。在心率恒定的情况下，硝苯地平显著抑制收缩，缩短动作电位持续时间并降低平台期高度。硝苯地平的这些作用与其他动物物种中维拉帕米的作用相似，结果支持钙拮抗剂除了对慢电流抑制的直接后果外可能还具有继发性细胞内作用的观点。
