Depolarization and insulin-like growth factor-I (IGF-I) differentially regulate the mitotic cycle in cultured rat sympathetic neuroblasts.

Although neuroblast generation is highly reproducible temporospatially, the underlying regulation is undefined. Employing a fully defined sympathetic neuroblast culture system, we previously found that insulin growth factors regulated the mitotic cycle. We now report that depolarizing stimuli, including elevated K+ and veratridine, also increased the proportion of mitotic neuroblasts in vitro. Moreover, Na+ channel blockade prevented effects of depolarization, but not that of insulin-like growth factor I, suggesting that these influences stimulate mitosis by different membrane transduction mechanisms.