title: Headache and mechanical sensitization of human pericranial muscles after repeated intake of monosodium glutamate (MSG).
abstract: BACKGROUND
  A single intake of monosodium glutamate (MSG) may cause headache and increased muscle sensitivity. We conducted a double-blinded, placebo-controlled, crossover study to examine the effect of repeated MSG intake on spontaneous pain, mechanical sensitivity of masticatory muscles, side effects, and blood pressure.
  
  
  METHODS
  Fourteen healthy subjects participated in 5 daily sessions for one week of MSG intake (150 mg/kg) or placebo (24 mg/kg NaCl) (randomized, double-blinded). Spontaneous pain, pressure pain thresholds and tolerance levels for the masseter and temporalis muscles, side effects, and blood pressure were evaluated before and 15, 30, and 50 min after MSG intake. Whole saliva samples were taken before and 30 min after MSG intake to assess glutamate concentrations.
  
  
  RESULTS
  Headache occurred in 8/14 subjects during MSG and 2/14 during placebo (P = 0.041). Salivary glutamate concentrations on Day 5 were elevated significantly (P < 0.05). Pressure pain thresholds in masseter muscle were reduced by MSG on Day 2 and 5 (P < 0.05). Blood pressure was significantly elevated after MSG (P < 0.040).
  
  
  CONCLUSIONS
  In conclusion, MSG induced mechanical sensitization in masseter muscle and adverse effects such as headache and short-lasting blood pressure elevation for which tolerance did not develop over 5 days of MSG intake.
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Vennelyst Boulevard 9, Aarhus C 8000, Denmark. akiko.shimada@odontologi.au.dk
authors.forename: Akiko
authors.initials: A
authors.lastname: Shimada
authors.forename: Brian E
authors.initials: BE
authors.lastname: Cairns
authors.forename: Nynne
authors.initials: N
authors.lastname: Vad
authors.forename: Kathrine
authors.initials: K
authors.lastname: Ulriksen
authors.forename: Anne Marie Lynge
authors.initials: AM
authors.lastname: Pedersen
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
authors.forename: Lene
authors.initials: L
authors.lastname: Baad-Hansen
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005503:Food Additives / Q000009:adverse effects*; D018698:Glutamic Acid / Q000032:analysis; D006261:Headache / Q000139:chemically induced*; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects*; D012463:Saliva / Q000737:chemistry; D012970:Sodium Glutamate / Q000009:adverse effects*
chemical_list: D005503:Food Additives; D018698:Glutamic Acid; D012970:Sodium Glutamate
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