title: Increased expression of cannabinoid CB₁ receptors in Achilles tendinosis.
abstract: BACKGROUND
  The endogenous cannabinoid system is involved in the control of pain. However, little is known as to the integrity of the cannabinoid system in human pain syndromes. Here we investigate the expression of the cannabinoid receptor 1 (CB₁) in human Achilles tendons from healthy volunteers and from patients with Achilles tendinosis.
  
  
  METHODS
  Cannabinoid CB₁ receptor immunoreactivity (CB₁IR) was evaluated in formalin-fixed biopsies from individuals suffering from painful Achilles tendinosis in comparison with healthy human Achilles tendons.
  
  
  RESULTS
  CB₁IR was seen as a granular pattern in the tenocytes. CB₁IR was also observed in the blood vessel wall and in the perineurium of the nerve. Quantification of the immunoreactivity in tenocytes showed an increase of CB₁ receptor expression in tendinosis tissue compared to control tissue.
  
  
  CONCLUSIONS
  Expression of cannabinoid receptor 1 is increased in human Achilles tendinosis suggesting that the cannabinoid system may be dysregulated in this disorder.
authors.affiliation: Pharmacology Unit, Department of Pharmacology and Clinical Neuroscience, Umeå University, Umeå, Sweden. emmelie.bjorklund@pharm.umu.se
authors.forename: Emmelie
authors.initials: E
authors.lastname: Björklund
authors.forename: Sture
authors.initials: S
authors.lastname: Forsgren
authors.forename: Håkan
authors.initials: H
authors.lastname: Alfredson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Fowler
mesh_terms: D000125:Achilles Tendon / Q000378:metabolism*; D000328:Adult; D000368:Aged; D005455:Fluorescent Antibody Technique; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D052256:Tendinopathy / Q000378:metabolism*; D055815:Young Adult
chemical_list: D043884:Receptor, Cannabinoid, CB1