DISTINCT ELECTRIC POTENTIALS IN SOMA AND NEURITE MEMBRANES

Structurally similar voltage-dependent ion channels may behave differe ntly in different locations along the surface of a neuron. A possible reason could be that channels experience nonuniform electrical potenti als along the plasmalemma. Here, we map the electrical potentials alon g the membrane of differentiated N1E-115 neuroblastoma cells with a po tential-sensitive dye. We find that the intramembrane potential gradie nt is indeed more positive in the membranes of neurites than in the me mbranes of somata. This is not attributable to differences in ion cond uctances or surface charge densities between the membranes of neurites and somata; instead, it can be explained by differences in lipid comp osition. The spatial variation in intramembrane electrical potential m ay help account for electrophysiological and functional differences be tween neurites and somata.