Perpendicular organization of sympathetic neurons within a required physiological voltage

In vitro, postganglionic sympathetic neurons (PSNs) profoundly organize their anatomy according to cues provided by an extracellular voltage. Over 90% of PSNs retract neurites that are parallel/tangential to a gradient of approximately 400 mV/mm. Complete neurite retraction takes approximately 20-40 minutes. Subsequently, neurites grow out from the soma, but now perpendicular to the lines of force while branching profusely. The complete restructuring of the neurons anatomy takes 2-3 hours at 35 degrees C. The maintenance of this asymmetrical anatomy requires the continuous presence of the extracellular electrical field (Ef). We discuss this observation relative to the organization of neurons residing in natural voltage gradients that exist across all epithelia in which neurons are born, mature, or migrate.