title: Sympathetic nerve responses to muscle contraction and stretch in ischemic heart failure.
abstract: Congestive heart failure (CHF) induces abnormal regulation of peripheral blood flow during exercise. Previous studies have suggested that a reflex from contracting muscle is disordered in this disease. However, there has been very little investigation of the muscle reflex regulating sympathetic outflows in CHF. Myocardial infarction (MI) was induced by the coronary artery ligation in rats. Echocardiography was performed to determine fractional shortening (FS), an index of the left ventricular function. We examined renal and lumbar sympathetic nerve activities (RSNA and LSNA, respectively) during 1-min repetitive (1- to 4-s stimulation to relaxation) contraction or stretch of the triceps surae muscles. During these interventions, the RSNA and LSNA responded synchronously as tension was developed. The RSNA and LSNA responses to contraction were significantly greater in MI rats (n = 13) with FS <30% than in control animals (n = 13) with FS >40% (RSNA: +49 +/- 7 vs. +19 +/- 4 a.u., P < 0.01; LSNA: +28 +/- 7 vs. +8 +/- 2 a.u., P < 0.01) at the same tension development. Stretch also increased the RSNA and LSNA to a larger degree in MI (n = 13) than in control animals (n = 13) (RSNA: +36 +/- 6 vs. +19 +/- 3 a.u., P < 0.05; LSNA: +24 +/- 3 vs. +9 +/- 2 a.u., P < 0.01). The data demonstrate that CHF exaggerates sympathetic nerve responses to muscle contraction as well as stretch. We suggest that muscle afferent-mediated sympathetic outflows contribute to the abnormal regulation of peripheral blood flow seen during exercise in CHF.
authors.affiliation: Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Koba
authors.forename: Jihong
authors.initials: J
authors.lastname: Xing
authors.forename: Lawrence I
authors.initials: LI
authors.lastname: Sinoway
authors.forename: Jianhua
authors.initials: J
authors.lastname: Li
mesh_terms: D000344:Afferent Pathways / Q000503:physiopathology; D000818:Animals; D001794:Blood Pressure; D003331:Coronary Vessels / Q000601:surgery; D004195:Disease Models, Animal; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D006339:Heart Rate; D006439:Hemodynamics; D007668:Kidney / Q000294:innervation / Q000503:physiopathology; D008026:Ligation; D008160:Lumbosacral Plexus / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction; D009470:Muscle Spindles / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation / Q000503:physiopathology*; D009203:Myocardial Infarction / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012026:Reflex, Stretch; D012039:Regional Blood Flow; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013710:Tendons / Q000294:innervation / Q000503:physiopathology; D013997:Time Factors; D014463:Ultrasonography; D016277:Ventricular Function, Left