Analgesic effect of Ga-Al-As diode laser irradiation on hyperalgesia in carrageenin-induced inflammation.
This study concerned the effect of Ga-Al-As diode laser irradiation (780 nm, continuous wave, 31.8 J/s/cm2, spot size od 0.2 mm, 3 minutes/dose) on hyperalgesia induced in the hind paw of rats by injecting carrageenin. The pressure-pain thresholds of hind paws were measured by the Randall-Selitto test for evaluation of hyperalgesia. Two doses of laser irradiation, given to the inflamed region immediately before and after the injection of carrageenin, partially (approximately 50%) inhibited the occurrence of hyperalgesia accompanied with a progression of inflammation. This analgesic effect was equal to that of indomethacin (4 mg/kg, i.o.). In another group, the hyperalgesia was removed almost completely for at least 24 hours by one dose of laser irradiation, which was given 3 hours after the carrageenin injection, whereas the edema was not inhibited. This analgesic effect, however, was partially (approximately 50%) antagonized with a dose of 10 mg/kg (i.p.) of naloxone and totally inhibited with 30 mg/kg. These results suggest that low-power laser irradiation on inflamed regions of carrageenin-treated rats has a marked analgesic effect and that certain mechanisms that are not related to endogenous opioids are involved in a part of the mechanisms of the analgesic effects.
Honmura
A
A
Kanagawa Rehabilitation Research Institute, Atsugi, Japan.
Ishii
A
A
Yanase
M
M
Obata
J
J
Haruki
E
E
D000698:Analgesia; D000818:Animals; D002351:Carrageenan; D006930:Hyperalgesia / Q000209:etiology / Q000517:prevention & control / Q000628:therapy*; D007213:Indomethacin / Q000627:therapeutic use; D007249:Inflammation / Q000139:chemically induced / Q000150:complications; D053685:Laser Therapy; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010147:Pain Measurement; D051381:Rats; D017208:Rats, Wistar
D009270:Naloxone; D002351:Carrageenan; D007213:Indomethacin