title: Nociceptive scores and endorphin-containing cells reduced by low-level laser therapy (LLLT) in inflamed paws of Wistar rat.
abstract: OBJECTIVE
  This study aimed to investigate how local pain relief is mediated by laser therapy and how dose affects the relationship.
  
  
  METHODS
  Inflammation was induced in the hind-paws of Wistar rats. Two groups of rats received 780-nm laser therapy (Spectra-Medics Pty Ltd.) at one of two doses (2.5 and 1 J/cm(2)). One group acted as a control. Scores of nociceptive threshold were recorded using paw pressure and paw thermal threshold measures.
  
  
  RESULTS
  A dose of 1 J/cm(2) had no statistically significant effect on antinociceptive responses. A dose of 2.5 J/cm(2) demonstrated a statistically significant effect on paw pressure threshold ( p < 0.029) compared to controls. There was no difference in paw thermal threshold responses and paw volumes at either dose. Immunohistochemistry in control animals demonstrated normal beta-endorphin containing lymphocytes in control inflamed paws but no beta-endorphin containing lymphocytes in rats that received laser at 2.5 J/cm(2).
  
  
  CONCLUSIONS
  The results confirm previous findings that the effect of laser therapy is dose-related. The mechanism of effect may occur via a differentiated pressure-sensitive neural pathway rather than a thermal-sensitive neural pathway. The significance of the immunohistochemistry findings remains unknown.
authors.affiliation: School of Physiotherapy and Exercise Science, Griffith University, Gold Coast Campus, PMB50 Gold Coast Mail Centre, Queensland 9726, Australia. l.laakso@griffith.edu.au
authors.forename: E-Liisa
authors.initials: EL
authors.lastname: Laakso
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Cabot
mesh_terms: D000818:Animals; D006614:Hindlimb / Q000378:metabolism* / Q000528:radiation effects; D007249:Inflammation / Q000532:radiotherapy*; D028022:Low-Level Light Therapy; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D010146:Pain / Q000532:radiotherapy; D017288:Pain Threshold; D011879:Radiotherapy Dosage; D051381:Rats; D017208:Rats, Wistar; D001615:beta-Endorphin / Q000378:metabolism*
chemical_list: D001615:beta-Endorphin