title: Growth effects of botulinum toxin type A injected into masseter muscle on a developing rat mandible.
abstract: OBJECTIVE
  Botulinum toxin type A (BTX-A) reduces the muscular contractions by temporarily inhibiting the release of acetylcholine at the neuromuscular junction. The purpose of this study was to investigate the effects of the BTX-A injected into the masseter muscle of a developing rat mandible.
  
  
  METHODS
  Four-week-old male (no. 80) Sprague-Dawley rats were divided into four groups: control group, saline group, BTX-A group and baseline control group. Rats of baseline group were sacrificed at 0 day to provide baseline values of the mandibular measurements. The masseter muscle of rats in the saline and the BTX-A group were administered with saline and BTX-A solutions respectively. Experimental animals were sacrificed after 4 weeks.
  
  
  RESULTS
  The BTX-A group demonstrated smaller mandibular dimension compared with the other groups (P < 0.05). Their condylar cartilages showed increased apoptosis at the proliferation stage of the reserve zone and masseter muscle fibers demonstrated atrophic changes.
  
  
  CONCLUSIONS
  The result demonstrated BTX-A influence on inhibitory action of the developing mandible because of apoptosis at the proliferation stage of the reserve zone of the condylar cartilage in developing rat mandible.
authors.affiliation: Department of Pediatric Dentistry, The Institute of Oral Health Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Kim
authors.forename: S-T
authors.initials: ST
authors.lastname: Kim
authors.forename: S-W
authors.initials: SW
authors.lastname: Cho
authors.forename: H-S
authors.initials: HS
authors.lastname: Jung
authors.forename: K-T
authors.initials: KT
authors.lastname: Park
authors.forename: H-K
authors.initials: HK
authors.lastname: Son
mesh_terms: D000818:Animals; D017209:Apoptosis; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000187:drug effects; D007273:Injections, Intramuscular; D008297:Male; D008334:Mandible / Q000187:drug effects* / Q000254:growth & development; D008335:Mandibular Condyle / Q000187:drug effects; D008406:Masseter Muscle / Q000187:drug effects; D008445:Maxillofacial Development / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D019274:Botulinum Toxins, Type A