title: Autonomic nerve activity and blood pressure in ambulatory dogs.
abstract: BACKGROUND
  The relationship between cardiac autonomic nerve activity and blood pressure (BP) changes in ambulatory dogs is unclear.
  
  
  OBJECTIVE
  The purpose of this study was to test the hypotheses that simultaneous termination of stellate ganglion nerve activity (SGNA) and vagal nerve activity (VNA) predisposes to spontaneous orthostatic hypotension and that specific β₂-adrenoceptor blockade prevents the hypotensive episodes.
  
  
  METHODS
  We used a radiotransmitter to record SGNA, VNA, and BP in eight ambulatory dogs. Video imaging was used to document postural changes.
  
  
  RESULTS
  Of these eight dogs, five showed simultaneous sympathovagal discharges in which the minute-by-minute integrated SGNA correlated with integrated VNA in a linear pattern (group 1). In these dogs, abrupt termination of simultaneous SGNA-VNA at the time of postural changes (as documented by video imaging) was followed by abrupt (>20 mm Hg over four beats) drops in BP. Dogs without simultaneous on/off firing (group 2) did not have drastic drops in pressure. ICI-118,551 (ICI, a specific β₂-blocker) infused at 3 µg/kg/h for 7 days significantly increased BP from 126 mm Hg (95% confidence interval 118-133) to 133 mm Hg (95% confidence interval 125-141; P = .0001). The duration of hypotension (mean systolic BP <100 mm Hg) during baseline accounted for 7.1% of the recording. The percentage was reduced by ICI to 1.3% (P = .01).
  
  
  CONCLUSIONS
  Abrupt simultaneous termination of SGNA-VNA was observed at the time of orthostatic hypotension in ambulatory dogs. Selective β₂-adrenoceptor blockade increased BP and reduced the duration of hypotension in this model.
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana.
authors.forename: Jessica
authors.initials: J
authors.lastname: Hellyer
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana; Division of Vascular Surgery, Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: A
authors.initials: A
authors.lastname: George Akingba
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana.
authors.forename: Kyoung-Suk
authors.initials: KS
authors.lastname: Rhee
authors.affiliation: Hunter Holmes McGuire VA Medical Center, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Alex Y
authors.initials: AY
authors.lastname: Tan
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Lane
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana; Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis, Indiana.
authors.forename: Changyu
authors.initials: C
authors.lastname: Shen
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana.
authors.forename: Jheel
authors.initials: J
authors.lastname: Patel
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana; Department of Pathology and Laboratory Medicine, University of California, Los Angeles, California.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Fishbein
authors.affiliation: Division of Cardiology, Department of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana. Electronic address: chenpp@iu.edu.
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
mesh_terms: D058672:Adrenergic beta-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D005260:Female; D006321:Heart / Q000294:innervation*; D007024:Hypotension, Orthostatic / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D013233:Stellate Ganglion / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D058672:Adrenergic beta-2 Receptor Antagonists
keywords: ANS; Ambulatory nerve recording; BP; Beta-blockade; HR; MSNA; Orthostatic hypotension; SGNA; VNA; autonomic nervous system; blood pressure; heart rate; iSGNA; iVNA; integrated stellate ganglion nerve activity; integrated vagal nerve activity; muscle sympathetic nerve activity; stellate ganglion nerve activity; vagal nerve activity