Simulation studies on the impact of the firing of action potential of myocytes with bipolar pulses

Abstract

Muscle contraction is one of puzzles for clinicians most eager to solve in the treatment of tumors during electroporation. The current measures to reduce muscle contraction, such as injection of muscle relaxation agents have certain side effects. Some studies suggest that bipolar pulse can effectively reduce muscle contraction, but the mechanism of this phenomenon is still unclear. Most exciting simulation studies concerning electrical activation of human muscles are based on the modeling approach of Hodgkin-Huxley model. For the study of bipolar pulse effect on action potential firing of myocytes from the point of excitability of myocytes, Simulink model of myocytes was established based on Hodgkin-Huxley model with Matlab. By comparing the different results that whether the action potential of myocytes is firing or not with the different conditions of myocytes that applying bipolar or unipolar pulses which both have the same duration of high level, we analyze the weakened effect of bipolar pulse on muscle contraction in the terms of the generation of the action potential of the myocytes. The results showed that for the same high level time for the two different pulses, the amplitude needed to fire the action potential of myocytes with bipolar pulses is significantly higher than the unipolar pulses, and this indicate that bipolar pulse can inhibit the firing of the action potential of myocytess. And in this way, the bipolar pulse can achieve the effect of weakening muscle contraction in terms of inhibition of transmembrane potential. In addition, we also find that when we apply bipolar pulses with short duration like 40us or 5us, there will be an incubation period before the potential appears. Through the preliminary animal experiments with tunable bipolar pulse source developed by our group, muscle contraction with bipolar pulses is weaken compared with unipolar pulse in the same amplitude of the two different pulses. Even in some cases, muscle contracts occur with unipolar pulses, while no shrinkage with bipolar pulses.