title: Cardiovascular responses elicited by continuous versus intermittent electrical stimulation of the aortic depressor nerve in conscious rats.
abstract: OBJECTIVE
  Short-term (seconds or minutes) continuous electrical activation of the aortic depressor nerve (ADN) in conscious rats has been successfully used to investigate baroafferent function in experimental hypertension, heart failure, and peripheral inflammation. The aim of this study was to characterize the hemodynamic responses elicited by longer periods (60min) of continuous or intermittent electrical baroreflex activation.
  
  
  METHODS
  Wistar rats were implanted with an electrode around the left ADN and a catheter into a femoral artery. The systolic, diastolic and mean arterial pressure and heart rate were recorded in subjects randomly assigned to continuous or intermittent electrical stimulation. The time-course of cardiovascular responses in conscious rats was examined during longer-term (60min) continuous (n=6) or intermittent (5s ON/3s OFF; n=10) electrical stimulation (0.5mA; 0.25ms; 30Hz) of the ADN.
  
  
  RESULTS
  The prompt (20s) hypotensive response was greater under continuous stimulation, but no difference was detected in the bradycardic response. The hypotensive response was sustained only by continuous stimulation while no sustained bradycardia was observed in either protocol.
  
  
  CONCLUSIONS
  These findings indicate that continuous stimulation of the ADN is more effective in reducing arterial pressure over a longer period (60min) of stimulation. Nevertheless, both protocols - continuous or intermittent - were unable to elicit a sustained bradycardia.
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Brognara
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Daniel P Martins
authors.initials: DP
authors.lastname: Dias
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Jaci A
authors.initials: JA
authors.lastname: Castania
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Rubens
authors.initials: R
authors.lastname: Fazan
authors.affiliation: Department of Pediatrics, Division of Pulmonology, Allergy and Immunology, Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lewis
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil. Electronic address: hcsalgado@fmrp.usp.br.
authors.forename: Helio C
authors.initials: HC
authors.lastname: Salgado
mesh_terms: D000818:Animals; D001011:Aorta / Q000294:innervation* / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001919:Bradycardia / Q000209:etiology / Q000503:physiopathology; D003243:Consciousness / Q000502:physiology*; D004558:Electric Stimulation / Q000009:adverse effects / Q000379:methods; D004567:Electrodes, Implanted; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
keywords: Aortic depressor nerve; Arterial pressure; Baroreflex; Conscious rats; Electrical stimulation; Heart rate