Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 294, Issue 1, Pages H311-H321Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00835.2007
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Funding
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R01HL060800, R01HL075533, R01HL078866] Funding Source: NIH RePORTER
- NHLBI NIH HHS [R01 HL078866, HL 060800, R01 HL 075533, HL 078866, R01 HL075533, R01 HL060800] Funding Source: Medline
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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.
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