Visible light regulates neurite outgrowth of nerve cells

The neurite outgrowth of PC12 cells on collagen-coated glass plates under light emitting diode (LED) irradiation at several wavelengths (i.e., 455, 470, 525, 600, 630, 880 and 945 nm) was investigated. No neurite outgrowth was observed during cultivation under irradiation from the lamp of an inverted light microscope through filters (yielding mixed light at ca. 525 nm and more than 800 nm), whereas neurite outgrowth was observed during cultivation in the dark. When these cells were irradiated with monochromatic LED light, neurite outgrowth was slightly, but not completely, suppressed at 455, 525, 600, 630, 880 and 945 nm, as was observed in the case of mixed light. Long connected neuronal outgrowths (e.g., 3 mm length) were observed with LED light at 470 nm and 1.8 mW/cm2 intensity. No such outgrowths were observed at other LED light wavelengths (i.e., 455, 525, 600, 630, 880 and 945 nm). Irradiation at 470 nm may have caused specific responses to transductional signals in these cells that led to the connection of neuronal outgrowths between cells. Not only suppressed neurite outgrowth but also long connected neurite outgrowths were observed when PC12 cells were cultured under several different wavelengths of light

Molecules that make axons grow.

The study of neurite growth in tissue culture has been a productive way to identify substances that may control the behavior of axons in vivo. Molecules that promote the outgrowth of neurites include nerve growth factor, laminin, fibronectin, and a protease inhibitor derived from glia. Evidence that these molecules may influence axon growth and guidance in vivo is discussed. The effects these molecules have at the cellular level are compared, in an attempt to identify common mechanisms of action. Several less well-characterized molecules that influence the behavior of neurites are also discussed