| Abstract
| - The effect of neurite outgrowth of PC12 cells on collagen-coated glass plates under intermittent light irradiationat 525 nm and 0.4 mW/cm2 of intensity was investigated. Neurite outgrowth of PC12 cells was significantlysuppressed when PC12 cells were cultivated under intermittent light irradiation with a total irradiation timeof more than 2 min/h. No temperature increase was observed in the culture medium under either continuousor intermittent light irradiation. Therefore, suppression of neurite outgrowth under light irradiation was notdue to the increase of temperature in the culture medium, but rather the effect of light on the PC12 cells,especially the signal transmittance of light to PC12 cells. The light irradiation interval also affected the neuriteoutgrowth of PC12 cells when the total irradiation time was constant. A high extension ratio of neurite outgrowthwas observed under a long time interval of nonirradiation between light irradiations (1 min of irradiationevery hour) as compared with frequent light irradiation intervals (5 s of irradiation every 5 min) with thesame total irradiation period per hour. The neurite outgrowth ratio was thought to be dependent on the lightintensity, the total time of light irradiation in the intermittent light irradiation, and the interval of light irradiationin the intermittent light irradiation.
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