Wollmer P, Wohlfart B, Khan A R
Acta Physiol Scand. 1981 Oct;113(2):183-7. doi: 10.1111/j.1748-1716.1981.tb06880.x.
The effects of 4-aminopyridine (4-AP) were studied on isolated papillary muscles from the heart of reserpinized rabbits (at 37 degrees C). The preparations were paced to contract at 0.67 Hz under isometric conditions and the muscle length was adjusted to 95% of the length for optimum force production. Simultaneous recordings of isometric force and membrane potentials were performed. 4-AP (50 microM) increased peak force by approximately 20% of the control and prolonged the action potential by 20%. Higher concentrations of 4-AP (800 microM) resulted in further increments of force and action potential duration (60 and 70% of controls, respectively). Prolongation of the action potential and potentiation of the isometric force was still present one hour after withdrawal of the drug from the perfusate. The results are consistent with the view that 4-AP prolongs the action potential by inhibiting the late repolarizing potassium current. It is suggested that the calcium uptake by the ventricular cell during the prolonged action potential is increased and that this leads to the positive inotropic effect.
研究了4-氨基吡啶（4-AP）对利血平化家兔心脏分离乳头肌（37℃）的作用。在等长条件下，将标本以0.67Hz的频率起搏收缩，并将肌肉长度调整至产生最佳力量的长度的95%。同时记录等长力和膜电位。4-AP（50μM）使峰值力增加约为对照的20%，并使动作电位延长20%。更高浓度的4-AP（800μM）导致力量和动作电位持续时间进一步增加（分别为对照的60%和70%）。从灌流液中撤药一小时后，动作电位延长和等长力增强仍然存在。结果与4-AP通过抑制晚期复极化钾电流来延长动作电位的观点一致。有人提出，在延长的动作电位期间心室细胞的钙摄取增加，这导致了正性肌力作用。
