A Dipole Model for Negative Steady-State Resistance in Excitable Membranes

Abstract

A dipole model is presented for ion flow in excitable membranes. This model considers the membrane to be composed of two distinct regions: a polar region and a nonpolar region. Further, the construction of an electrodiffusive formalism which takes explicit account of the energy of partition required by an ion for passage from external fluid to nonpolar region is presented. In the polar region a cooperative effect is considered which produces a configurational transition of the polar group dependent only on membrane voltage. A resulting change in voltage drop across the polar group is brought about by this configurational transition. This gives rise to a negative steady-state resistance for the equimolar case, in reasonable agreement with observation. The theory, in addition, is in reasonable accord with nonequimolar ion flow, and provides an explanation for such effects as the following: the intercept of the voltage-current characteristic, the ion membrane concentrations inferred from electrodiffusion theories, and the effects of polyvalent cations

The effect of holding potential on the asymmetry currents in squid giant axons

“…852 0 II H. ME VES ASYMMETRY CURRENTS IN GIANT AXONS 83 electric field and has been applied to the nerve membrane by previous authors (e.g. Hamel & Zimmerman, 1970). In this equation x = (gtE/IT) where /et = dipole moment, E = potential gradient across the membrane (calculated for a 70 A thick membrane), k = Boltzmann constant and T = absolute temperature.…”

The effect of temperature on the asymmetrical charge movement in squid giant axons.

“…The temperature dependence of Qon, Qoff could be simply due to the increase of membrane fluidity with increasing temperature (see review of Chapman (1975) and measurements of Cossins & Prosser (1978) on synaptosomal membranes); an increase in fluidity would lead to greater rotational freedom for the polar molecules in the membrane. Hamel & Zimmerman (1970) have suggested that, as the temperature increases, more and more dipoles in the nerve membrane may become free to rotate because thermal motion reduces the number of dipoles in the original plane and thereby weakens the restoring dipole-dipole forces (order-disorder transition).…”

Polarization kinks and propagation of action potential in axon membranes

“…It has been suggested that ion channels might have a polarization of electret or ferroelectric origin [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Summarized below are the following facts supporting the hypothesis of ferroelectricity in sodium channels.…”