title: Effects of repeated atropine injection on heart rate variability in Thoroughbred horses.
abstract: To investigate the effects of repeated atropine injection on heart rate (HR) variability in resting Thoroughbred horses, two microg/ kg of atropine as parasympathetic nervous blockade was injected intravenously every 6 min to a total of 8 microg/kg after intravenous administration of 0.2 mg/kg of propranolol as sympathetic nervous blockade. We recorded electrocardiograms and obtained the HR, then evaluated variation in HR from the power spectrum in terms of low frequency (LF, 0.01-0.07 Hz) power and high frequency (HF, 0.07-0.6 Hz) power. Administration of atropine decreased parasympathetic nervous activity in a dose-dependent manner, affecting first the LF power, then the HF power and finally HR. These responses may provide valuable information for evaluating autonomic nervous activity in Thoroughbred horses.
authors.affiliation: Equine Science Division, Hidaka Yearling Training Farm of Japan Racing Association, Urakawa-gun, Hokkaido, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ohmura
authors.forename: A
authors.initials: A
authors.lastname: Hiraga
authors.forename: H
authors.initials: H
authors.lastname: Aida
authors.forename: M
authors.initials: M
authors.lastname: Kuwahara
authors.forename: H
authors.initials: H
authors.lastname: Tsubone
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D001341:Autonomic Nervous System / Q000502:physiology; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006736:Horses / Q000502:physiology*; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology*; D011433:Propranolol / Q000008:administration & dosage
chemical_list: D000319:Adrenergic beta-Antagonists; D010276:Parasympatholytics; D001285:Atropine; D011433:Propranolol