Effects of near-infrared low-level laser irradiation on microcirculation

Background and Objective: Recently, there has been an increase in the clini cal application of low-level laser irradiation (LLLI) in various fields. Th e present study was conducted to explore the effects of LLLI on microcircul ation. Study Design/Material and Methods: We investigated the effects of LLLI on r at mesenteric microcirculation in vivo, and on cytosolic calcium concentrat ion ([Ca2+]i) in rat vascular smooth muscle cells (VSMCs) in vitro. Results: LLLI caused potent dilation in the laser-irradiated arteriole, whi ch led to marked increases in the arteriolar blood flow. The changes were p artly attenuated in the initial phase by the superfusion of 15 muM L-NAME, but they were not affected by local denervation. Furthermore, LLLI caused a power-dependent decrease in [Ca2+]i in VSMCs. Conclusion: The circulatory changes observed seemed to be mediated largely by LLLI-induced reduction of [Ca2+]i in VSMCs, in addition to the involveme nt of NO in the initial phase. Lasers Surg. Med. 27:427-437, 2000. (C) 2000 Wiley-Liss, Inc.