title: Age-related sensitivity to nicotine for inducible atrial tachycardia and atrial fibrillation.
abstract: The influence of nicotine in modulating vulnerability to atrial tachycardia and fibrillation (AT/AF) remains ill defined. The isolated hearts of six young (2-3 mo) and six old (22-24 mo) male Fischer 344 rats were Langendorff perfused at 5 ml/min with oxygenated Tyrode solution at 37 degrees C, and the whole heart was also super-fused with warmed oxygenated Tyrode solution at 15 ml/min. Nicotine prolonged the interatrial conduction time and effective refractory period that were significantly (P < 0.05) higher in the old than in the young rats in a concentration-dependent manner. Nicotine had a biphasic effect on burst atrial pacing-induced AT in both groups, increasing it at 10-30 ng/ml while decreasing it at 50-100 ng/ml (P < 0.01). Nicotine at 10-100 ng/ml increased burst atrial pacing-induced AF in the young rats but suppressed it in the old rats (P < 0.01). Optical mapping showed the presence of multiple independent wavefronts during AF and a single periodic large wavefront during AT in both groups. Nicotine, at concentrations found in the blood of smokers (30-85 ng/ml), exerts biphasic effects on inducible AT/AF in young rats and suppresses it in the old rats by causing high degrees of interatrial conduction block.
authors.affiliation: Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90048, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Chikaya
authors.initials: C
authors.lastname: Omichi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: William J
authors.initials: WJ
authors.lastname: Mandel
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
authors.forename: Hrayr S
authors.initials: HS
authors.lastname: Karagueuzian
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001281:Atrial Fibrillation / Q000139:chemically induced / Q000503:physiopathology*; D001835:Body Weight; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D009929:Organ Size; D010138:Pacemaker, Artificial; D051381:Rats; D011916:Rats, Inbred F344; D013612:Tachycardia, Ectopic Atrial / Q000139:chemically induced / Q000503:physiopathology*
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine