title: Inhibition of neuronal nitric oxide reduces heart rate variability in the anaesthetised dog.
abstract: In the vagally intact anaesthetised dog, we have investigated the role of nitric oxide (NO) on a normal sinus arrhythmia using an inhibitor of neuronally released NO, 1-(2-trifluoromethylphenyl) imidazole (TRIM). The mean and S.D. of the R-R interval was used to describe mean heart rate and heart rate variability, respectively. TRIM (0.8 mg I.C.) injected into the sinus node artery increased the mean heart rate slightly but reduced heart rate variability 3-fold from a control of 790 +/- 124 ms (mean +/- S.D.; n = 5) to 666 +/- 36 ms (P < 0.01 Student's paired t test, n = 5). These results suggest that neuronally released NO may have a vagal facilitatory role in the maintenance of sinus arrhythmia in the normal heart.
authors.affiliation: Department of Physiology, University College Cork, Cork, Ireland. hazim@ucc.ie
authors.forename: F
authors.initials: F
authors.lastname: Markos
authors.forename: H M
authors.initials: HM
authors.lastname: Snow
authors.forename: C
authors.initials: C
authors.lastname: Kidd
authors.forename: K
authors.initials: K
authors.lastname: Conlon
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000758:Anesthesia; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001262:Atenolol / Q000494:pharmacology; D001794:Blood Pressure; D004285:Dogs / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000502:physiology*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D014630:Vagus Nerve / Q000187:drug effects / Q000378:metabolism
chemical_list: D000889:Anti-Arrhythmia Agents; D004791:Enzyme Inhibitors; D007093:Imidazoles; C098186:1-(2-trifluoromethylphenyl)imidazole; D009569:Nitric Oxide; D001262:Atenolol; D019001:Nitric Oxide Synthase; D000109:Acetylcholine