Effects of low-level laser energy of microcirculation

The physiological basis of low-level laser treatment (LLLT), which is widely used in pain clinic practice(1), was investigated with special reference to microcirculation. Male Wistar rats were used. The tow-level laser was irradiated on the mesenteric arteriole about 20 mu m in diameter for five minuets and red cell velocity (V-RBC), microvessel diameter (D) and volumetric blood flow (Q) (calculated with V-RBC and D) were measured at pre and post laser irradiation. Q rapidly increased in 1 min after laser irradiation (early phase) and slowly increased for 5 to 20 min until it reached plateau by 30 min. These changes were not affected by denervation, but superfusion of L-NAME suppressed the increase of Q at early phase. The results suggest the involvement of nitric oxide (NO) in the increase of Q by low-level laser irradiation.