title: Vagal nerve stimulation increases right ventricular contraction and relaxation and heart rate.
abstract: OBJECTIVE
  To determine the effects of vasoactive intestinal peptide, released from the right and left vagal nerves, on ventricular contraction, relaxation, and heart rate.
  
  
  METHODS
  The muscarinic and beta-adrenergic receptors were blocked with atropine and propranolol, and afterload was controlled in 48 anesthetized, open-chest mongrel dogs. Experiments were performed in the absence (Series 1, 10 dogs) and in the presence (Series 2, 22 dogs) of a controlled heart rate and prior to and after the administration of a sensitive and selective vasoactive intestinal peptide antagonist (Series 3, 16 dogs).
  
  
  RESULTS
  Right ventricular contraction (+dp/dtmax), relaxation (-dp/dtmin) and heart rate increased significantly during 20 Hz vagal nerve stimulation for 5 min. Vagal nerve stimulation in Series 1 increased right ventricular +dp/dtmax by 28% from a control value of 480 +/- 11 (P < 0.001) and right ventricular -dp/dtmin by 23% from a control value of 341 +/- 11 (P < 0.002). Left ventricular +dp/dtmax and -dp/dtmin increased slightly but not significantly. Vagal nerve stimulation also increased the heart rate by 29% from a control value of 149 +/- 2 (P < 0.001). During controlled heart rate in Series 2, vagal nerve stimulation at 20 Hz consistently increased right ventricular +dp/dtmax and -dp/dtmin comparable to Series 1 experiments but did not increase left ventricular +dp/dtmax or -dp/dtmin. Injection of the vasoactive intestinal peptide antagonist [4Cl-DPhe6, Leu17]VIP into the right coronary artery of 16 dogs in Series 3 did not affect right ventricular +dp/dtmax, -dp/dtmin, or heart rate. However, this antagonist substantially decreased the vagal-induced increases in right ventricular +dp/dtmax, -dp/dtmin, and heart rate by 85, 63, and 71% (P < 0.005), respectively.
  
  
  CONCLUSIONS
  The present experiments suggest that vagal nerve stimulation releases vasoactive intestinal peptide (VIP) or a "VIP-like substance' that significantly increases right ventricular contraction, relaxation, and heart rate.
authors.affiliation: University of South Florida College of Medicine, Division of Cardiology, Tampa, FL, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Henning
authors.forename: L
authors.initials: L
authors.lastname: Feliciano
authors.forename: C M
authors.initials: CM
authors.lastname: Coers
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006727:Hormone Antagonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D018005:Receptors, Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors; D014630:Vagus Nerve / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000031:analogs & derivatives* / Q000494:pharmacology; D016278:Ventricular Function, Right / Q000502:physiology*
chemical_list: D000319:Adrenergic beta-Antagonists; D006727:Hormone Antagonists; D018727:Muscarinic Antagonists; D018005:Receptors, Vasoactive Intestinal Peptide; C048507:vasoactive intestinal peptide, 4-chloro-Phe(6)-Leu(17)-; D014660:Vasoactive Intestinal Peptide; D001285:Atropine; D011433:Propranolol