Therapeutic effect of Ga-Al-As diode laser irradiation on experimentally induced inflammation in rats

We produced experimental inflammation models in rats by carrageenin and studied the effect of Ga‐Al‐As diode laser irradiation (780 nm, continuous wave, 31.8 j/sec/cm2, spot size of 0.2 mm) on inflamed regions compared with those of indomethacin, a potent anti‐inflammatory agent. We found that a low‐power infrared laser has an anti‐inflammatory effect on carrageenin inflammation. A low‐power laser inhibits: (1) the increase of vascular permeability during the occurrence of an acute inflammation in the carrageenin‐air‐pouch model, (2) edema in the acute stage in the carrageenin‐paw‐edema model, and (3) the granuloma formation in the carrageenin‐granuloma model after receiving laser irradiation once daily. In all cases, irradiation for less than 10 min was sufficient to inhibit the inflammation by 20–30%. The inhibitory effect of laser irradiation was not comparable to that of indomethacin (4 mg/kg, i.o.) in the air‐pouch model and the paw‐edema model, whereas laser irradiation was more potent than that of daily administration of indomethacin (1 mg/kg, i.o.) in the granuloma model. In future studies of the mechanism of laser effect, it should be noted that irradiating a rat twice, before and after the provocation of inflammation, was essential in order to achieve an effective inhibition of paw‐edema. © 1992 Wiley‐Liss, Inc.