Sympathetic responses to exercise in myocardial infarction rats: a role of central command

Abstract

Koba, Satoshi, Zhaohui Gao, Jihong Xing, Lawrence I Sinoway, and Jianhua Li. Sympathetic responses to exercise in myocardial infarction rats: a role of central command. Am J Physiol Heart Circ Physiol 291: H2735-H2742, 2006. First published July 14, 2006 doi:10.1152/ajpheart.00522.2006.-In congestive heart failure (CHF), exaggerated sympathetic activation is observed during exercise, which elicits excess peripheral vasoconstriction. The mechanisms causing this abnormality are not fully understood. Central command is a central neural process that induces parallel activation of motor and cardiovascular systems. This study was undertaken to determine whether central command serves as a mechanism that contributes to the exaggerated sympathetic response to exercise in CHF. In decerebrated rats, renal and lumbar sympathetic nerve responses (RSNA and LSNA, respectively) to 30 s of fictive locomotion were examined. The fictive locomotion was induced by electrical stimulation of the mesencephalic locomotor region (MLR). The study was performed in control animals (fractional shortening Ͼ 40%) and animals with myocardial infarctions (MI; fractional shortening Ͻ 30%). With low stimulation of the MLR (current intensity ϭ 20 A), the sympathetic responses were not significantly different in the control (RSNA: ϩ18 Ϯ 4%; LSNA: ϩ3 Ϯ 2%) and MI rats (RSNA: ϩ16 Ϯ 5%; LSNA: ϩ8 Ϯ 3%). With intense stimulation of the MLR (50 A), the responses were significantly greater in MI rats (RSNA: ϩ127 Ϯ 15%; LSNA: ϩ57 Ϯ 10%) than in the control rats (RSNA: ϩ62 Ϯ 5%; LSNA: ϩ21 Ϯ 6%). In this study, the data demonstrate that RSNA and LSNA responses to intense stimulation of the MLR are exaggerated in MI rats. We suggest that intense activation of central command may play a role in evoking exaggerated sympathetic activation and inducing excessive peripheral vasoconstriction during exercise in CHF.congestive heart failure; mesencephalic locomotor region; renal sympathetic nerve activity; lumbar sympathetic nerve activity EXERCISE ACTIVATES THE SYMPATHETIC nervous system, increases blood pressure, and leads to an increase in blood flow to exercising skeletal muscle. This increase in muscle blood flow is associated with reduced renal blood flow (23). Two principal neural mechanisms are proposed to increase sympathetic nerve activity (SNA) and regulate the cardiovascular system during exercise. These are termed the exercise pressor reflex and central command. The exercise pressor reflex is a neural reflex that arises from receptors sensitive to mechanical and metabolic stimuli in exercising skeletal muscles and stimulates the medulla through the muscle thin afferent fibers (18). Central command is a feed-forward neural mechanism that induces parallel activation of motor and cardiovascular systems (9, 50). The brain sites that generate motor signals also send descending projections to sympathetic neurons (19,20,22).Congestive heart failure (CHF) includes abnormal cardiovascular regulation in exercise. Specifically, sympathetic tone to muscle is elevat...

Cardiac autonomic modulation during progressive upper limb exercise by patients with coronary artery disease

“…It is well accepted that autonomic modulation of HR during exercise is mediated by a central command, exercise pressor reflex and arterial baroreflex (31)(32)(33). However, the findings of Koba et al (34) suggest that an intensive activation of the central command occurs in myocardial infarction (MI) and leads to an excessive sympathetic outflow. In this context, after acute MI there is a prevalence of sympathetic tonus, which is similar to our finding that suggested overactivity of sympathetic modulation in individuals who suffered MI (CADG).…”

Femoral artery occlusion augments TRPV1-mediated sympathetic responsiveness

“…Renal SNA (RSNA) was recorded as previously described (16,17). Briefly, a bundle of the renal nerves was carefully dissected from other connective tissues.…”

Neural Regulation of Cardiovascular Response to Exercise: Role of Central Command and Peripheral Afferents

“…However, few studies to date have investigated the role of central command. Koba et al employed decerebration in rats, and then electrically stimulated the mesencephalic locomotor area, inducing fictive locomotion [73]. They noted that renal and lumbar sympathetic nerve activity increased exaggeratedly in rats with heart failure during intense stimulation of the mesencephalon.…”