Objective To study the electrophysiological characteristics of early-differentiated neural stem cells(NSC)in embryonic rats.Methods NSC were isolated from hippocampus of embryonic rats and cultured.The cells were plated onto poly-llysine hydrochloride glass cover-slips for 1 h or differentiated for 1-3 d in a differentiation medium.Whole cell patch-clamp technique was used to record the voltage-gated ion channel current.Results No inward Na+ current was detected in any undifferentiated NSC.One day after induction of differentiation,the cells exhibited a voltage-gated Na+ current,but could not induce an action potential.Two types of outward K+ current(delayed rectifier K+ and transient K+ current) and inward T-type Ca2+ current were detected in NSC and early-differentiated NSC.Conclusion The functional expression of Na+ current is a marker of early differentiation of NSC following cell cycle exit.Early differentiation of NSC is an important development stage of their ion channels.