Nonlinear cell response to strong electric fields

The response of living cells to externally applied electric fields is of wi despread interest. In particular; the intensification of electric fields ac ross cell membranes is believed to be responsible, through membrane rupture and reversible membrane breakdown processes, for certain types of tissue d amage in electrical trauma cases which cannot be attributed to Joule heatin g. Large elongated cells such as skeletal muscle fibres are particularly vu lnerable to such damage. Previous theoretical studies of field intensificat ion across cell membranes in such cells have assumed the membrane current t o be linear in the applied field (Ohmic membrane conductivity) and were lim ited to sinusoidal applied fields. In this paper, we investigate a simple m odel of a long cylindrical cell, corresponding to nerve or skeletal muscle cells. Employing the electroquasistatic approximation, a system of coupled first-order differential equations for the membrane electric field is deriv ed which incorporates arbitrary time dependence in the external held and no nlinear membrane response (non-Ohmic conductivity). The behaviour of this m odel is investigated for a variety of applied fields in both the linear and highly nonlinear regimes. We find that peak membrane fields predicted by t he nonlinear model are approximately twice as intense, For low-frequency el ectrical trauma conditions, as those of the linear theory.