A combined experimental and computational analysis of membrane potential variations in excitable cells in response to DC electric fields

Two approaches were used to gain an understanding of the spatial variations in membrane potential resulting from exposure of cultured adrenal medullary chromaffin cells to a 20 V/cm DC electric field of different orientations. The finite element method was used to solve Poisson's equation for the potential in a Petri dish containing isolated spherical chromaffin cells or chromaffin cell aggregates of various configurations and the results of the computations were compared to the results obtained experimentally. The latter used fluorescence imaging of chromaffin cell membranes stained with the fluorescent voltage-sensitive dye di-8-ANEPPS to monitor variations in membrane potential. For single cells, the numerical results for membrane potential variation were in good agreement with the experimental results. For realistic chains of two or three cells, the results from both methods were in agreement only when the long axis of the chain was perpendicular to the electric field. For three cells forming a realistic, irregularly shaped aggregate, variations in membrane potential determined experimentally were more complex than those predicted by the numerical computations for regions of cell contact. The results provide a foundation for understanding how excitable cells respond to DC electric fields and identify parameters that influence these responses.