title: Dynamic exercise training prevents exercise pressor reflex overactivity in spontaneously hypertensive rats.
abstract: Cardiovascular responses to exercise are exaggerated in hypertension. We previously demonstrated that this heightened cardiovascular response to exercise is mediated by an abnormal skeletal muscle exercise pressor reflex (EPR) with important contributions from its mechanically and chemically sensitive components. Exercise training attenuates exercise pressor reflex function in healthy subjects as well as in heart failure rats. However, whether exercise training has similar physiological benefits in hypertension remains to be elucidated. Thus we tested the hypothesis that the EPR overactivity manifest in hypertension is mitigated by exercise training. Changes in mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in response to muscle contraction, passive muscle stretch, and hindlimb intra-arterial capsaicin administration were examined in untrained normotensive Wistar-Kyoto rats (WKYUT; n = 6), exercise-trained WKY (WKYET; n = 7), untrained spontaneously hypertensive rats (SHRUT; n = 8), and exercise-trained SHR (SHRET; n = 7). Baseline MAP after decerebration was significantly decreased by 3 mo of wheel running in SHRET (104 ± 9 mmHg) compared with SHRUT (125 ± 10 mmHg). As previously reported, the pressor and renal sympathetic responses to muscle contraction, stretch, and capsaicin administration were significantly higher in SHRUT than WKYUT. Exercise training significantly attenuated the enhanced contraction-induced elevations in MAP (SHRUT: 53 ± 11 mmHg; SHRET: 19 ± 3 mmHg) and RSNA (SHRUT: 145 ± 32%; SHRET: 57 ± 11%). Training produced similar attenuating effects in SHR during passive stretch and capsaicin administration. These data demonstrate that the abnormally exaggerated EPR function that develops in hypertensive rats is significantly diminished by exercise training.
authors.affiliation: Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; masaki.mizuno@utsouthwestern.edu.
authors.forename: Masaki
authors.initials: M
authors.lastname: Mizuno
authors.affiliation: Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas; and.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Iwamoto
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Hypertension Section, Cardiology Division, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Wanpen
authors.initials: W
authors.lastname: Vongpatanasin
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
authors.forename: Jere H
authors.initials: JH
authors.lastname: Mitchell
authors.affiliation: Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
authors.forename: Scott A
authors.initials: SA
authors.lastname: Smith
mesh_terms: D000818:Animals; D001794:Blood Pressure; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D005082:Physical Exertion; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012018:Reflex; D013564:Sympathetic Nervous System / Q000502:physiology
keywords: blood pressure; exercise pressor reflex; exercise training; hypertension; sympathetic nerve activity