Nerve growth factor (NGF) induces neuritelike process outgrowth in cultured adult pancreatic beta cells. DbcAMP partially mimics this effect on cell morphology, and both compounds act synergistically to promote neuritelike process outgrowth. To determine if NGF- and dbcAMP-induced differentiation was accompanied by changes in beta cell electrical activity, we studied the macroscopic Na current of adult rat beta cells identified with the reverse hemolytic plaque assay and cultured for one week with these factors. After 5-7 days, beta cells cultured in the presence of 2.5S NGF exhibited a 48% increase on the macroscopic Na current, which was due to an increase on Na current density. We did not observe changes on voltage dependence of current activation, nor on steady-state inactivation. Although dbcAMP also promotes changes on beta cell morphology, it did not affect the Na current density.