title: Contrasting effects of moderate vagal stimulation on heart rate and carotid sinus baroreflex-mediated sympathetic arterial pressure regulation in rats.
abstract: OBJECTIVE
  To examine whether moderate efferent vagal nerve stimulation (VNS) attenuates the carotid sinus baroreflex-mediated arterial pressure (AP) regulation via its antagonism to the sympathetic system.
  
  
  METHODS
  Carotid sinus baroreceptor regions were isolated from the systemic circulation in eight anesthetized and vagotomized rats. A staircase-wise input was imposed on carotid sinus pressure (CSP) with or without efferent VNS (20Hz, 2ms, 1-4V), while the responses in AP, heart rate (HR), and splanchnic sympathetic nerve activity (SNA) were measured.
  
  
  RESULTS
  A multiple linear regression analysis indicated that VNS decreased the minimum HR in the CSP-HR relationship by 58.2±4.9 beats/min (P<0.01) from its reference value of 387.0±5.8 beats/min. Although VNS significantly decreased an intercept of the SNA-AP relationship, it did not affect parameters of the CSP-AP relationship or the CSP-SNA relationship significantly. The operating-point AP of the baroreflex was decreased by 2.8±1.0mmHg (P<0.01) during VNS, which was less than 3% of the reference value of 117.7±1.2mmHg.
  
  
  CONCLUSIONS
  VNS, at an intensity of decreasing HR by approximately 13%, does not acutely attenuate the baroreflex-mediated sympathetic AP regulation.
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center Research Institute, Osaka 565-8565, Japan. torukawa@res.ncvc.go.jp
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Shuji
authors.initials: S
authors.lastname: Shimizu
authors.forename: Meihua
authors.initials: M
authors.lastname: Li
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kamiya
authors.forename: Kazunori
authors.initials: K
authors.lastname: Uemura
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sata
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
mesh_terms: D000818:Animals; D017704:Baroreflex; D001794:Blood Pressure; D002346:Carotid Sinus / Q000294:innervation*; D006339:Heart Rate; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology; D055536:Vagus Nerve Stimulation