title: Influence of botulinum toxin on rabbit jaw muscle activity and anatomy.
abstract: BACKGROUND
  Muscles can adapt their fiber properties to accommodate to new conditions. We investigated the extent to which a decrease in muscle activation can cause an adaptation of fiber properties in synergistic and antagonistic jaw muscles.
  
  
  METHODS
  Three months after the injection of botulinum toxin type A in one masseter (anterior or posterior) muscle changes in fiber type composition and fiber cross-sectional areas in jaw muscles were studied at the microscopic level.
  
  
  RESULTS
  The injected masseter showed a steep increase in myosin type IIX fibers, whereas fast fibers decreased by about 50% in size. Depending on the injection site, both synergistic and antagonistic muscles showed a significant increase in the size of their fast IIA fibers, sometimes combined with an increased number of IIX fibers.
  
  
  CONCLUSIONS
  Silencing the activity in the masseter not only causes changes in the fibers of the injected muscle but also leads to changes in other jaw muscles.
authors.affiliation: Department of Oral Cell Biology and Functional Anatomy, ACTA, University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands. j.korfage@acta.nl
authors.forename: J A M
authors.initials: JA
authors.lastname: Korfage
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Wang
authors.forename: S H J T J
authors.initials: SH
authors.lastname: Lie
authors.forename: Geerling E J
authors.initials: GE
authors.lastname: Langenbach
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D004558:Electric Stimulation; D004576:Electromyography; D007839:Functional Laterality; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects*; D009465:Neuromuscular Agents / Q000494:pharmacology*; D011817:Rabbits; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A