title: Potentiated sympathetic nervous and renin-angiotensin systems reduce nonlinear correlation between sympathetic activity and blood pressure in conscious spontaneously hypertensive rats.
abstract: BACKGROUND
  Patients with a reduced nonlinear component of heart rate regulation have a poorer outcome.
  
  
  RESULTS
  We investigated whether a nonlinear correlation between renal sympathetic nerve activity (RSNA) and blood pressure or renal blood flow is reduced in conscious, spontaneously hypertensive rats (SHR) by comparing them with normotensive Wistar-Kyoto rats (WKY). We also determined the linearity and nonlinearity of the correlation in SHR who were given an angiotensin II receptor blocker, candesartan, orally for 2 weeks. The RSNA value was higher in SHR than in WKY, and coherence peaks of transfer function were found at 0.05 and 0.80 Hz (ie, below respiratory- and cardiac-related fluctuations). The coherence (linearity) of the transfer function was significantly higher and gain was smaller in SHR than in WKY. Because mutual information values (linear and nonlinear correlation) were similar in both strains, we found the nonlinear correlation to be lower in SHR than in WKY. Time delay values calculated by the mutual information method demonstrated that RSNA preceded blood pressure and renal blood flow by 0.5 to 1.0 s. In SHR given candesartan, the RSNA value was lower, and the linearity was lower and nonlinearity higher than SHR given vehicle.
  
  
  CONCLUSIONS
  Linear correlation between RSNA and blood pressure or renal blood flow was higher in SHR than in WKY, whereas the nonlinear correlation was lower. Oral treatment with candesartan increased the nonlinearity and reduced the linearity in SHR. Increased RSNA and the renin-angiotensin system may be responsible for the lower nonlinearity and higher linearity in hypertension.
authors.affiliation: Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Katsufumi
authors.initials: K
authors.lastname: Sakata
authors.forename: Hiroo
authors.initials: H
authors.lastname: Kumagai
authors.forename: Motohisa
authors.initials: M
authors.lastname: Osaka
authors.forename: Toshiko
authors.initials: T
authors.lastname: Onami
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Matsuura
authors.forename: Masaki
authors.initials: M
authors.lastname: Imai
authors.forename: Takao
authors.initials: T
authors.lastname: Saruta
mesh_terms: D000284:Administration, Oral; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001120:Arginine / Q000008:administration & dosage; D001562:Benzimidazoles / Q000008:administration & dosage; D001713:Biphenyl Compounds; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004562:Electrocardiography / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007668:Kidney / Q000098:blood supply / Q000187:drug effects / Q000294:innervation; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012084:Renin-Angiotensin System / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D013777:Tetrazoles / Q000008:administration & dosage; D014851:Wakefulness
chemical_list: D057911:Angiotensin Receptor Antagonists; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D013777:Tetrazoles; D001120:Arginine; C081643:candesartan