title: A direct inhibitory effect of botulinum toxin type A on antral circular muscle contractility of guinea pig.
abstract: OBJECTIVE
  Recent studies suggest new mechanisms of Botulinum toxin (BoNT) other than inhibiting acetylcholine (ACh) release from nerve terminals. The aim of this study was to determine whether other mechanisms for BoNT exist, so that it directly inhibits smooth muscle contraction.
  
  
  METHODS
  Guinea pig antral muscle strips were studied in vitro after 2 hours of exposure to Botulinum toxin type A (BoNT/A). Contractile responses to electric field stimulation (EFS), high K(+) (60 mM) and ACh (100 μM) were evaluated 24 and 48 hours after antral intramuscular injection of BoNT/A or vehicle.
  
  
  RESULTS
  BoNT/A inhibited muscular contraction caused by high K(+) and ACh. Contractile responses to low (1 and 4 Hz) and high (8 and 20 Hz) frequency EFS of antral muscle strips 24 and 48 hours after antral intramuscular injection of BoNT/A were significantly inhibited.
  
  
  CONCLUSIONS
  The ability of BoNT/A to directly inhibit antral muscular contractility suggests a new mechanism for the pharmacologic actions of BoNT-direct inhibition of muscular contraction.
authors.affiliation: Department of Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Park
authors.forename: Eunjoo
authors.initials: E
authors.lastname: Choi
authors.forename: Hyojin
authors.initials: H
authors.lastname: Park
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D011706:Pyloric Antrum / Q000187:drug effects
chemical_list: D019274:Botulinum Toxins, Type A