Develop Of Single Cell Electrophysiology Simulation Software And Simulation Study Of Action Potentials In Rat Adrenal Chromaffin Cells

Electrical behavior in live cells, which based on the physical activity of ion channels, is one of essential characters of life. The study on ion channels, therefore, has remarkable impact on disease treatment and drug discovery. A variety of abnormal phenotypes including epilepsy, ataxia, vascular hypertension and long QT have more or less relationship with structural change of channel proteins. As a typical kind of electrical excitable cells, chromaffin cells play an important role in neural incretion. There are many kinds of ion channels in chromaffin cells which can regulate the excitability. Each kind of channels plays an unique and significant role during action potential firing, and modulates the firing frequency, amplitude and half width. However, the precise mechanisms of regulating action potential are still not clear.This dissertation focuses on the regulation of action potentials by BK_i, BK_S, K_V channels and Na channels with bi-exponential recovery feature in rat adrenal medulla chromaffin cells, using electrophysiological techniques and computational simulation methods.First, we develop a single cell electrophysiology simulation environment, named CeL, based on allosteric model of channel proteins. It breaks through the limitation of H-H-like equation(s) which can not describe the complex molecular mechanism of gating, implementing allosteric model by computational algorithm, integrating several channel models into a specific cell model, and then simulates both channel gating processing and cell electrical activities modulating by variety of channels. This is an innovation in using computational methods in the field of electrophysiology research. Based on the simulation of patch clamp, we enhance the ability of CeL in automatic constructing conformational allosteric model and automatic data processing. Automatic constructing model module can give the computational optimization parameters for conformational allosteric model, which is collected manually in the world until now. Automatic data processing module can deal with batch of data at the same time, therefore, it greatly improves the efficient of data processing, and it is also the first one on the earth.Second, we refer some literature and use CeL to analysis amount of experimental data to acquire the channel models.Finally, using the well defined channel models, we can play the whole cell electronical behavior simulation. By simulating action potentials under different cell environments and comparing the experimental data analyzing, we can investigate the different regulation by different channels in the cell.Based on our experimental data and simulation, we can conclude:1. BK current can modify hyperpolarization and afterhyperpolarization during the action potential.2. Cumulative inactivation of BK_i current can only be obvious in higher [Ca²⁺]_i, otherwise it exhibits little.3. The key functional difference between BKj and BKs current, which accounts for the remarkable differential firing is not inactivation, but the more easily activation for BK_i current at a given [Ca²⁺].4. The Ca²⁺-dependence of AP firing in native RCC and simulated model cells suggests that there is little K_V channel in chromaffin cells, which can contribute on only one firing of action potential. Excessive could result in abnormal firing.5. K_V current contributes on the beginning of repolarization and rapid hyperpolarization phase during the action potential.6. The bi-exponential recovery property can help keeping the firing frequency and amplitude of action potential.In summary, our study clearly demonstrates the functions and contributions of these channels during AP firing, it could provide meanful suggestions for disease study and drug discovery. Meanwhile, as an innovation software suite, CeL expands the technique of biophysical study and greatly improves the efficiency of research.