title: Ionic mechanisms underlying the effects of vasoactive intestinal polypeptide on canine atrial myocardium.
abstract: BACKGROUND
  Vasoactive intestinal polypeptide (VIP) is released from intracardiac neurons during vagal stimulation, ischemia, and heart failure, which are associated with increased vulnerability to atrial fibrillation. VIP shortens atrial effective refractory periods in dogs. Endogenous VIP contributes to vagally mediated acceleration of atrial electric remodeling. VIP is also shown to prolong the duration of acetylcholine-induced atrial fibrillation. However, the ionic mechanisms underlying VIP effects are largely unknown.
  
  
  RESULTS
  The effects of VIP on transmembrane ion channels were studied in canine atrial cardiomyocytes using patch-clamp techniques. VIP increased delayed rectifier K+ current and L-type calcium current but decreased the transient outward K+ current and sodium current. Optical mapping technique was used to assess effects of VIP on action potential durations (APDs) in isolated canine left atria. VIP shortened APD and slowed conduction velocity in a dose-dependent manner. Furthermore, VIP increased spatial heterogeneity of APD and conduction velocity, as assessed by the SDs of APD and conduction velocity, and atrial fibrillation inducibility.
  
  
  CONCLUSIONS
  Through its diverse effects on ion channels, VIP shortens APD with increased APD spatial heterogeneity and decreases intra-atrial conduction velocity, which may play an important role in the pathogenesis of atrial arrhythmias in scenarios where VIP release is increased.
authors.affiliation: Texas Heart Institute/St. Luke's Episcopal Hospital, Houston.
authors.forename: Yutao
authors.initials: Y
authors.lastname: Xi
authors.forename: Geru
authors.initials: G
authors.lastname: Wu
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ai
authors.forename: Nancy
authors.initials: N
authors.lastname: Cheng
authors.forename: Jurij Matija
authors.initials: JM
authors.lastname: Kalisnik
authors.forename: Junping
authors.initials: J
authors.lastname: Sun
authors.forename: Shahrzad
authors.initials: S
authors.lastname: Abbasi
authors.forename: Donghui
authors.initials: D
authors.lastname: Yang
authors.forename: Christopher
authors.initials: C
authors.lastname: Fan
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Yuan
authors.forename: Suwei
authors.initials: S
authors.lastname: Wang
authors.forename: MacArthur
authors.initials: M
authors.lastname: Elayda
authors.forename: Igor D
authors.initials: ID
authors.lastname: Gregoric
authors.forename: Bharat K
authors.initials: BK
authors.lastname: Kantharia
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
mesh_terms: D000200:Action Potentials; D000818:Animals; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000503:physiopathology*; D015220:Calcium Channels / Q000378:metabolism; D004285:Dogs; D006325:Heart Atria / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology*; D006329:Heart Conduction System / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D014660:Vasoactive Intestinal Peptide
keywords: action potentials; atrial fibrillation; ion channels; vasoactive intestinal polypeptide