School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
Ann Biomed Eng. 2011 Jan;39(1):96-109. doi: 10.1007/s10439-010-0160-x. Epub 2010 Sep 17.
In this study, the relationships between the early and late afterpotentials and velocity and amplitude recovery functions (VRF and ARF) in skeletal muscle were examined using model simulation. A mathematical model of the muscle fiber action potential, that incorporated a tubular slow potassium conductance, was developed and used to simulate muscle fiber action potentials at a range of interpulse intervals. The slow potassium conductance produced an afterhyperpolarization which resulted in supernormal action potential conduction velocity and amplitude for interpulse intervals>7 ms. Increasing the number of conditioning stimuli caused a further increase in conduction velocity and amplitude, and an additional phase of supernormality, with a peak at approximately 100 ms. Positive correlations between instantaneous firing rate and both conduction velocity and amplitude were also observed during simulation of repetitive stimulation of the muscle fiber. The relationships were eliminated when the slow potassium conductance channel was removed from the model. The results suggest that an afterhyperpolarization, possibly due to a slow tubular potassium conductance, could cause the VRF and ARF observed in muscle. They additionally suggest that the positive correlations between instantaneous firing rate, conduction velocity, and amplitude are directly related to the VRF and ARF.
在这项研究中，使用模型模拟检查了骨骼肌中早期和晚期后电位与速度和幅度恢复功能（VRF 和 ARF）之间的关系。开发了一种包含管状慢钾电导的肌肉纤维动作电位数学模型，并用于模拟一系列脉冲间隔下的肌肉纤维动作电位。慢钾电导产生后超极化，导致脉冲间隔>7 毫秒时动作电位传导速度和幅度超正常。随着条件刺激次数的增加，传导速度和幅度进一步增加，并出现另一个超正常阶段，在大约 100 毫秒时达到峰值。在模拟肌肉纤维重复刺激时，还观察到瞬时放电率与传导速度和幅度之间存在正相关关系。当从模型中去除慢钾电导通道时，这种关系就会消失。研究结果表明，后超极化可能是由于慢管状钾电导引起的，可能导致肌肉中观察到的 VRF 和 ARF。此外，还表明瞬时放电率、传导速度和幅度之间的正相关关系与 VRF 和 ARF 直接相关。
