[The effect of laser irradiation on arthritis in rats]

Based on the analgesic effect of laser therapy in clinic, the effect of laser irradiation at acupoints on the experimental arthritis in rats was further observed. The experiments were carried out on Wistar rats, which were divided into three groups: The normal group (n = 6): without any treatment. The laser group (n = 8): 24 hours after an injection of Freund's adjuvant, the typical symptoms of acute arthritis (red, swelling, pain and hyperalgesia) occurred. Then transcutaneous irradiation with a low power Helium-neon laser (3 mw, 6328 A) at ipsilateral Kun-Lun point was applied ten minutes every day for five days. The control group (n = 8): with the same treatment as the laser group except laser irradiation. All the indexes, such as foot volume, pain score and pain threshold (Heat-leg-withdrawal latency, HWL and electric-shock vocalization, VOC) were measured every day. Comparing with the symptoms in the control group, the intensity of pain as measured on pain score and the swelling of the ankles (foot volume) were significantly reduced by laser irradiation (P less than 0.01), but the pain threshold (HWL and VOC) did not show any improvement in laser group. However, immediately after laser irradiation, the average pain threshold (VOC) was significantly raised (P less than 0.01). It is concluded that low power laser irradiation at local points can produce the relief from arthralgia and reduction in the swelling of ankles, and it can also produce instant analgesic effect in test of pain threshold (VOC).