n spotted on the target plate. Analysis of peptide masses was performed as described previously using MALDITOF MS. 2-DE protein patterns in TM, CWP and CON The protein pattern in the dialysate from CON was almost similar to the pattern in TM and in CWP. Higher numbers 
of protein spots could be detected in TM compared to CWP gel and the healthy control gel. Forty-eight out of 262 proteins in TM and 30 out of 196 proteins in CWP had concentrations at least twofold higher or lower than in CON. Seventeen of these proteins showed alterations in the concentrations both in TM 21990348 and CWP when compared to CON. Twelve out of the 17 proteins were altered in a similar way or lower ) in both groups of patients compared to CON: 1. 2. 3. 3 Database searches LC-MS/MS spectra were processed by Bruker Daltonics DataAnalysis 3.4 and resulting MS/MS data were searched in NCBInr and Swiss-Prot database on MASCOT server. Database search parameters were set as follows: the enzyme trypsin was used; up to one missed cleavage was allowed; fixed modification included were carbamidomethylation of cysteine and oxidation of Apolipoprotein AI Rho GDP-dissociation inhibitor2 Alpha-1-antitrypsin Proteomics of Trapezius Muscle Microdialysate 4. 5. 6. 7. 8. 9. 10. 11. 12. Protein S100-A9 Host cell factor C1 regulator 1 Carbonic anhydrase 3 Hemoglobin subunit beta Flavin reductase Flavin reductase Serum albumin Serum albumin Serotransferrin N N N N The alterations of the remaining five proteins were different in the two groups when compared to CON: 1. 2. 3. 4. 5. Alpha-1-antitrypsin Alpha-1-antitrypsin Actin, aortic smooth muscle ) Carbonic anhydrase 3 ) Alpha-1-antitrypsin A large number of proteins were found in the 18690793 interstitium of human muscles using MD in combination with 2-DE analysis. The identified proteins were proteins involved in inflammatory processes and metabolic, structural, regulatory, contractile and MedChemExpress SB366791 transporter proteins. Considerable proportions of the identified proteins were at least two-fold higher or lower in TM and CWP than in CON. The two groups of patients showed at least two-fold alterations in concentrations of the same proteins when compared to CON; approx 2/3 of these alterations were in the same direction. Discussion We, for the first time to the best of our knowledge, have described the molecular pattern of protein expression in human muscle microdialysate by using two dimensional gel electrophoresis in combination with mass spectrometry. To investigate the possibility that specific proteins in muscle dialysate samples might be markers of the different pain conditions, we analyzed proteins that were changed two folds or more between the three groups. Pronounced alterations in the proteome in the myalgic muscle of the two common chronic pain conditions were found. Hence, major results were: There is a need to understand the activated nociceptive mechanisms at various levels of the pain systems in chronic myalgia. In the present study we have focused upon peripheral alterations and collected dialysate from the interstitium of the trapezius. Earlier MD studies have reported peripheral alterations in concentrations of algesic, metabolic and antinociceptive substances; see for a review. However, these studies have, due to the small volumes of dialysate obtained from the muscle interstitium, only been able to analyze a few substances. The present technique, combining MD, 2-DE analysis and nLC-MS/ MS, opens up for an explorative approach not focusing u
