title: Differential response of pig masseter to botulinum neurotoxin serotypes a and b.
abstract: BACKGROUND
  Pigs respond to direct administration of botulinum neurotoxins (BoNTs), although they are resistant to botulism. The human masseter is frequently targeted for BoNT therapy. We aimed to understand how BoNT affects chewing by injecting porcine masseters.
  
  
  METHODS
  One masseter of minipigs was injected with BoNT serotype A or B at doses comparable to those used in humans. Masticatory function was evaluated electromyographically. Muscle force was measured during tetany. Four weeks after injection, strain gauges affixed to the mandible assessed bone strain during chewing. Masseter mass and fiber diameter were measured after euthanasia.
  
  
  RESULTS
  BoNT-A had no measurable effect. In contrast, BoNT-B reduced electrical activity and muscle force, producing substantial asymmetry between injected and uninjected muscles.
  
  
  CONCLUSIONS
  The pig masseter is highly resistant to direct injection of BoNT-A, but it is affected by BoNT-B.
authors.affiliation: Department of Orthodontics, University of Washington, Box 357446, Seattle, WA, 98195-7446, USA.
authors.forename: Zi-Jun
authors.initials: ZJ
authors.lastname: Liu
authors.affiliation: Department of Orthodontics, University of Washington, Box 357446, Seattle, WA, 98195-7446, USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Rafferty
authors.affiliation: Department of Orthodontics, University of Washington, Box 357446, Seattle, WA, 98195-7446, USA.|Department of Stomatology, No. 451 Hospital of PLA, Xi'an, P.R. China.
authors.forename: Wenmin
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Orthodontics, University of Washington, Box 357446, Seattle, WA, 98195-7446, USA.
authors.forename: Susan W
authors.initials: SW
authors.lastname: Herring
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects; D005260:Female; D007839:Functional Laterality; D008406:Masseter Muscle / Q000187:drug effects*; D009465:Neuromuscular Agents / Q000494:pharmacology*; D018709:Statistics, Nonparametric; D013552:Swine; D013997:Time Factors
chemical_list: D009465:Neuromuscular Agents; C096323:rimabotulinumtoxinB; D019274:Botulinum Toxins, Type A
keywords: botulinum neurotoxin; masseter; mastication; muscle atrophy; pig