title: Differential effects of repetitive oral administration of monosodium glutamate on interstitial glutamate concentration and muscle pain sensitivity.
abstract: OBJECTIVE
  The aim of this study was to determine the relationship of high daily monosodium glutamate (MSG) consumption with glutamate concentrations in jaw muscle, saliva, and serum, and muscle pain sensitivity in healthy participants.
  
  
  METHODS
  A randomized, double-blinded, placebo-controlled study was conducted to investigate the effect of repetitive consumption of high-dose MSG on glutamate concentration in the masseter muscles measured by microdialysis and muscle pain sensitivity. In five contiguous experimental daily sessions, 32 healthy participants drank MSG (150 mg/kg) or NaCl (24 mg/kg) diluted with a 400 mL soda. The concentrations of glutamate before and after the ingestion were assessed in dialysate and plasma samples on the first and last days. Saliva glutamate concentration was assessed every day. Pressure pain threshold, pressure pain tolerance, autonomic parameters (heart rate, systolic and diastolic blood pressures) and reported side effects also were assessed.
  
  
  RESULTS
  No significant change was noted in the baseline concentration of glutamate in the masseter muscle, blood, or saliva, but the peak concentration in the masseter muscle increased significantly between day 1 and 5. A statistically significant increase in systolic and diastolic blood pressures after MSG administration was observed, as well as a significantly higher frequency of reports of nausea and headache in the MSG group. No robust effect of MSG on muscle sensitivity was found.
  
  
  CONCLUSIONS
  Interstitial glutamate concentration in the masseter muscle is not highly disturbed by excessive repetitive intake of MSG in healthy man.
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON). Electronic address: akiko.shimada@odontologi.au.dk.
authors.forename: Akiko
authors.initials: A
authors.lastname: Shimada
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON).
authors.forename: Lene
authors.initials: L
authors.lastname: Baad-Hansen
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON).
authors.forename: Eduardo
authors.initials: E
authors.lastname: Castrillon
authors.affiliation: Department of Medical and Health Sciences, Rehabilitation Medicine, Faculty of Health Sciences, Linköping University & Pain and Rehabilitation Centre, County Council of Östergötland, Linköping, Sweden; Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine, Faculty of Health Sciences, Linköping University and Centre of Occupational and Environmental Medicine, County Council of Östergötland, Linköping, Sweden.
authors.forename: Bijar
authors.initials: B
authors.lastname: Ghafouri
authors.affiliation: Department of Medical and Health Sciences, Rehabilitation Medicine, Faculty of Health Sciences, Linköping University & Pain and Rehabilitation Centre, County Council of Östergötland, Linköping, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Stensson
authors.affiliation: Department of Medical and Health Sciences, Rehabilitation Medicine, Faculty of Health Sciences, Linköping University & Pain and Rehabilitation Centre, County Council of Östergötland, Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
authors.affiliation: Scandinavian Center for Orofacial Neurosciences (SCON); Section of Orofacial Pain and Jaw Function, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Ernberg
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Brian
authors.initials: B
authors.lastname: Cairns
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON).
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson Odont
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight; D015930:Diet Records; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005971:Glutamates / Q000737:chemistry*; D006261:Headache / Q000209:etiology / Q000473:pathology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects* / Q000503:physiopathology; D009325:Nausea / Q000209:etiology / Q000473:pathology; D017288:Pain Threshold / Q000187:drug effects*; D012463:Saliva / Q000737:chemistry; D012970:Sodium Glutamate / Q000008:administration & dosage* / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D005971:Glutamates; D012970:Sodium Glutamate
keywords: Diet; Mechanical muscle sensitivity; Microdialysis; Monosodium glutamate; Myofascial temporomandibular disorders; Pain