title: Obesity depresses baroreflex control of renal sympathetic nerve activity and heart rate in Sprague Dawley rats: role of the renal innervation.
abstract: OBJECTIVE
  This study investigated the role of the renal innervation in arterial and cardiopulmonary baroreflex regulation of renal sympathetic nerve activity (RSNA) and heart rate (HR) in rats fed a high-fat diet to induce obesity.
  
  
  METHODS
  Rats received either a normal (12% kcal) or high (45% kcal) fat diet for 60 days. On day 61, rats were anesthetized and prepared for recording left RSNA. In one group, the renal nerves remained intact, while in the other, both kidneys were denervated. Baroreflex gain curves for RSNA and HR were generated by increasing and decreasing blood pressure. Low-pressure baroreceptors were challenged by infusing a saline load.
  
  
  RESULTS
  Mean blood pressure was 135 mmHg in the fat-fed and 105 mmHg (P < 0.05) in normal rats. Weight gain, adiposity index and creatinine clearance were 37, 82 and 55% higher (P < 0.05-0.001), but urine flow rate and fractional sodium excretions were 53 and 65% (both P < 0.001) lower, respectively, in the fat-fed compared to normal rats. In fat-fed rats with innervated kidneys, RSNA and HR arterial baroreflex sensitivities were reduced by 73 and 72% (both P < 0.05) but were normal in renally denervated rats. Volume expansion decreased RSNA by 66% (P < 0.001) in normal rats, but not in the intact fat-fed rats and by 51% (P < 0.01) in renally denervated fat-fed rats.
  
  
  CONCLUSIONS
  Feeding a high-fat diet caused hypertension associated with dysregulation of the arterial and cardiopulmonary baroreflexes which was dependent on an intact renal innervation. This suggests that in obese states neural signals arising from the kidney contribute to a deranged autonomic control.
authors.affiliation: Department of Physiology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: S A
authors.initials: SA
authors.lastname: Khan
authors.affiliation: Department of Physiology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: M Z A
authors.initials: MZ
authors.lastname: Sattar
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur, Malaysia.
authors.forename: N A
authors.initials: NA
authors.lastname: Abdullah
authors.affiliation: Department of Physiology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: H A
authors.initials: HA
authors.lastname: Rathore
authors.affiliation: Department of Physiology, University College Cork, Cork, Ireland.
authors.forename: M H
authors.initials: MH
authors.lastname: Abdulla
authors.affiliation: Department of Physiology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: A
authors.initials: A
authors.lastname: Ahmad
authors.affiliation: Department of Physiology, University College Cork, Cork, Ireland.
authors.forename: E J
authors.initials: EJ
authors.lastname: Johns
mesh_terms: D000818:Animals; D017704:Baroreflex; D001794:Blood Pressure; D006339:Heart Rate; D007668:Kidney / Q000294:innervation / Q000503:physiopathology*; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000503:physiopathology*
keywords: baroreflex gain curves; cardiopulmonary reflex; high-fat diet