title: High levels of N-palmitoylethanolamide and N-stearoylethanolamide in microdialysate samples from myalgic trapezius muscle in women.
abstract: BACKGROUND
  N-acylethanolamines (NAEs) are endogenous compounds that regulate inflammation and pain. These include the cannabinoid ligand anandamide (AEA) and the peroxisome proliferator-activated receptor-α ligand palmitoylethanolamide (PEA). Little is known as to the levels of NAEs in pain states in human, particularly in the skeletal muscle. The aim of this study was to investigate the levels of these lipid mediators in muscle dialysate from women with chronic neck-/shoulder pain compared to healthy controls.
  
  
  METHODS
  Eleven women with chronic neck-/shoulder pain and eleven healthy women participated in this study. All participants went through microdialysis procedures in the trapezius muscle. Muscle dialysate samples were collected during four hours and analysed by nano liquid chromatography tandem mass spectrometry (nLC-MS/MS).
  
  
  RESULTS
  We were able to detect AEA, PEA, N-stearoylethanolamine (SEA) and 2-arachidonoylglycerol (2-AG) in a single chromatographic run. Of the NAEs studied, PEA and SEA were clearly detectable in the muscle microdialysate samples. The muscle dialysate levels of PEA and SEA were significantly higher in myalgic subjects compared to healthy controls.
  
  
  CONCLUSIONS
  This study demonstrates that microdialysis in combination with mass spectrometry can be used for analysing NAE's in human muscle tissue regularly over time. Furthermore the significant group differences in the concentration of PEA and SEA in this study might fill an important gap in our knowledge of mechanisms in chronic myalgia in humans. In the long run this expanded understanding of nociceptive and anitinociceptive processes in the muscle may provide a base for ameliorating treatment and rehabilitation of pain.
authors: Rehabilitation Medicine, Faculty of Health Sciences, Linköping University, and Pain and Rehabilitation Centre, County Council of Östergötland, Linköping, Sweden.
authors: Nazdar
authors: N
authors: Ghafouri
authors: Bijar
authors: B
authors: Ghafouri
authors: Britt
authors: B
authors: Larsson
authors: Maria V
authors: MV
authors: Turkina
authors: Linn
authors: L
authors: Karlsson
authors: Christopher J
authors: CJ
authors: Fowler
authors: Björn
authors: B
authors: Gerdle
mesh_terms: D000328:Adult; D000577:Amides; D002853:Chromatography, Liquid / Q000379:methods; D059350:Chronic Pain / Q000209:etiology / Q000378:metabolism; D015314:Dialysis Solutions / Q000737:chemistry*; D063388:Endocannabinoids; D004983:Ethanolamines; D005260:Female; D006801:Humans; D017551:Microdialysis; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D009135:Muscular Diseases / Q000150:complications / Q000378:metabolism; D036103:Nanotechnology / Q000379:methods; D019547:Neck Pain / Q000209:etiology / Q000378:metabolism; D010169:Palmitic Acids / Q000032:analysis / Q000378:metabolism*; D020069:Shoulder Pain / Q000209:etiology / Q000378:metabolism; D013229:Stearic Acids / Q000032:analysis / Q000378:metabolism*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D000577:Amides; D015314:Dialysis Solutions; D063388:Endocannabinoids; D004983:Ethanolamines; D010169:Palmitic Acids; D013229:Stearic Acids; C466089:stearoylethanolamide; C005958:palmidrol