System identification of electrically coupled smooth muscle cells: the passive electrical properties.

A system model approach based on a network model is used to investigate the passive electrical properties of coupled smooth muscle cells. This approach makes use of a gradient method of optimization to estimate the passive electrical parameters directly from the magnitude of the input impedance or voltage transfer function of the network model. The need for subjective measurements of parameters and many intermediate steps involved in the analysis using the conventional signal model approach are eliminated. The coupling resistance and capacitance are estimated with sound theoretical and mathematical grounds directly from experimental data. From the simulated results using SPICE, it is evident that the system model approach is accurate, flexible, and reproducible. These properties grant the new approach excellent potential for future studies of drug actions on smooth muscle cells and their associated electrical coupling. Also, sensitivities of the network model with respect to its parameters can readily be obtained. This may provide new insight into the coupling mechanisms of smooth muscle cells.