title: Acute effects of intravenous nifedipine or azelnidipine on open-loop baroreflex static characteristics in rats.
abstract: OBJECTIVE
  To assess the acute effects of intravenous azelnidipine, a third-generation L-type calcium channel blocker, on sympathetic outflow from the central nervous system and to compare the effects of intravenous azelnidipine with those of intravenous nifedipine.
  
  
  METHODS
  In anesthetized Wistar Kyoto rats, carotid sinus baroreceptor regions were isolated. Changes in sympathetic nerve activity (SNA) and arterial pressure (AP) in response to a stepwise baroreceptor pressure input were examined before and during intravenous nifedipine or azelnidipine (for each: 100 μg/kg bolus followed by 300 μg/kg/h infusion, n = 6).
  
  
  RESULTS
  Nifedipine significantly reduced the range of the AP response from 76.8 ± 7.4 to 45.4 ± 7.0 mmHg (P < 0.01) but did not affect the range of the SNA response (from 84.4 ± 5.1 to 85.9 ± 10.2%) or the SNA maximum gain (from 2.26 ± 0.28 to 2.35 ± 0.55%/mmHg). Similarly, azelnidipine significantly reduced the range of the AP response from 62.4 ± 3.9 to 31.4 ± 4.1 mmHg (P<0.01) but did not affect the range of the SNA response (from 71.2 ± 5.5 to 74.9 ± 7.2%) or the SNA maximum gain (from 1.64 ± 0.17 to 2.08 ± 0.26%/mmHg).
  
  
  CONCLUSIONS
  A depressor dose of nifedipine or azelnidipine does not have an acute sympathoinhibitory effect in normotensive Wistar Kyoto rats even when the level of SNA was varied over the entire operating range of the carotid sinus baroreflex.
authors.affiliation: Division of Cardiology, Department of Medicine, Faculty of Medicine, Kinki University, Osaka 589-8511, Japan. Electronic address: hiromi@med.kindai.ac.jp.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kamiya
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Turner
authors.affiliation: Division of Cardiology, Department of Medicine, Faculty of Medicine, Kinki University, Osaka 589-8511, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Miyazaki
authors.affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
mesh_terms: D061605:Administration, Intravenous; D000818:Animals; D001383:Azetidinecarboxylic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000493:pharmacokinetics*; D002346:Carotid Sinus / Q000502:physiology*; D004095:Dihydropyridines / Q000494:pharmacology*; D008297:Male; D009543:Nifedipine; D011311:Pressoreceptors / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY
chemical_list: D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D001383:Azetidinecarboxylic Acid; D009543:Nifedipine; C061679:azelnidipine
keywords: Azelnidipine; Carotid sinus baroreflex; Nifedipine; Open-loop system analysis; Sympathetic nerve activity