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The purpose of this study was to compare the effects of growth factors and 810-nm-wavelength light on the differentiation of normal human neural progenitor cells (NHNPCs) in vitro. Although growth factors are routinely used to study neural stem and progenitor cells in vitro, to date, light has not been used as a replacement for growth factors. This study demonstrates that NHNPCs are not only capable of being sustained by light in the absence of growth factors, but that they are also able to differentiate normally as assessed by neurite formation. The NHNPCs had an up-regulation in the expression of endogenous fibroblast growth factor-2, brain derived neurotrophic factor, and nerve growth factor in response to the light. Suramin, a nonselective P2 receptor antagonist, significantly decreased neurite outgrowth, and P2Y2 and P2Y11 receptors were found to be expressed by the NHNPCs by immunolabeling. Based on these findings, the mechanism by which light supports the NHNPC differentiation is hypothesized to be due to increases in adenosine triphosphate acting via P2Y receptors.