Analgesic effect of Ga-Al-As diode laser irradiation on hyperalgesia in carrageenin-induced inflammation

Lasers Surg Med. 1993;13(4):463-9. doi: 10.1002/lsm.1900130411.


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.

MeSH terms

  • Analgesia*
  • Animals
  • Carrageenan
  • Hyperalgesia / etiology
  • Hyperalgesia / prevention & control
  • Hyperalgesia / therapy*
  • Indomethacin / therapeutic use
  • Inflammation / chemically induced
  • Inflammation / complications
  • Laser Therapy*
  • Male
  • Naloxone / pharmacology
  • Pain Measurement
  • Rats
  • Rats, Wistar


  • Naloxone
  • Carrageenan
  • Indomethacin