title: Exercise training normalizes the blunted central component of the baroreflex in rats with heart failure: role of the PVN.
abstract: Exercise training (ExT) normalizes the increased sympathetic outflow in chronic heart failure (HF). The underlying mechanisms are not clearly understood. We hypothesized that ExT normalized the blunted central component of the baroreflex control of renal sympathetic nerve activity (RSNA) in HF. Four groups of rats [sham operated (sham)-sedentary (Sed), sham-ExT, HF-Sed, and HF-ExT] were used. HF was induced by left coronary artery ligation, and ExT consisted of 3 wk of treadmill running. In anesthetized rats, the decrease in RSNA in response to aortic depressor nerve stimulation (5-40 Hz) in the HF-Sed group was significantly lower than that in the sham-Sed group (-37 ± 7% vs. -63 ± 8% at 40 Hz, P < 0.05). In the HF-ExT group, responses in RSNA, mean arterial pressure (MAP), and heart rate (HR) were not significantly different from those in the sham-Sed or sham-ExT groups. ExT normalized blunted RSNA, MAP, and HR responses to bicuculline microinjections into the paraventricular nucleus (PVN) in rats with HF. Activation of the PVN by blockade of GABA receptors with bicuculline in normal control rats blunted the centrally component of the baroreflex arc. GABAA-α1 and -β1 receptor protein expression were significantly lower (by 48% and 30%) in the HF-Sed group, but ExT normalized this difference between the HF and sham groups. These data suggest that one mechanism by which ExT alleviates elevated sympathetic outflow in HF may be through normalization of central integrative mechanisms, perhaps via improving the inhibitory GABAergic mechanism within the PVN, on the baroreflex arc.
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA. kpatel@unmc.edu
authors.forename: Kaushik P
authors.initials: KP
authors.lastname: Patel
authors.forename: Helio C
authors.initials: HC
authors.lastname: Salgado
authors.forename: Xuefei
authors.initials: X
authors.lastname: Liu
authors.forename: Hong
authors.initials: H
authors.lastname: Zheng
mesh_terms: D000818:Animals; D062186:Arterial Pressure; D017704:Baroreflex / Q000187:drug effects; D004195:Disease Models, Animal; D004558:Electric Stimulation; D005081:Exercise Therapy; D018756:GABA Antagonists / Q000008:administration & dosage; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D007668:Kidney / Q000098:blood supply*; D008297:Male; D008845:Microinjections; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism; D020127:Recovery of Function; D012021:Reflex, Abnormal / Q000187:drug effects; D057185:Sedentary Behavior; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D018756:GABA Antagonists; C546242:Gabra1 protein, rat; C546267:Gabrb1 protein, rat; D011963:Receptors, GABA-A
keywords: aortic depressor nerve; blood pressure; paraventricular nucleus; sympathetic outflow; γ-aminobutyric acid receptor