The mechanism by which electrical stimulation affects formation of neuromuscular junctions (NMJs) remains unknown. NG108-15, a neural cell line, is commonly used in in vitro co-culture models of myotubes to observe synapse formation; therefore, we employed this model to observe the effects of electrical stimulation on NMJ formation. Initially, L6 cells were differentiated and NG108-15 cells were then added to the same culture dish. After 2 and 3 days of co-culture, the cells were electrically stimulated at 50 V and 0.5 Hz for 0, 5, 30, and 60 min (C, ES5, ES30, and ES60 groups, respectively) and were analyzed after co-culture for 4 days. Immunofluorescence experiments showed significantly increased aggregation of acetylcholine receptors and inhibition of neural outgrowth in the ES30 and ES60 groups. Furthermore, ADAM19 and phospho-ErbB3 were found to be specifically localized in co-cultured NG108-15 cells. Immunoblotting demonstrated that synapsin 1, ADAM19 precursor and its activated form, phospho-ErbB3, and ERK1 protein levels had increased in an electrical stimulation period-dependent manner. Thus, we found that electrical stimulation accelerated NMJ formation, possibly through activation of ADAM19/neuregulin/ErbB signaling in NG108-15 cells.
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