title: Altered firing pattern of single-unit muscle sympathetic nerve activity during handgrip exercise in chronic heart failure.
abstract: Sympathetic activation in chronic heart failure (CHF) is greatly augmented at rest but the response to exercise remains controversial. We previously demonstrated that single-unit muscle sympathetic nerve activity (MSNA) provides a more detailed description of the sympathetic response to physiological stress than multi-unit nerve recordings. The purpose of this study was to determine whether the reflex response and discharge properties of single-unit MSNA are altered during handgrip exercise (HG, 30% of maximum voluntary contraction for 3 min) in CHF patients (New York Heart Association functional class II or III, n = 16) compared with age-matched healthy control subjects (n = 13). At rest, both single-unit and multi-unit indices of sympathetic outflow were augmented in CHF compared with controls (P < 0.05). However, the percentage of cardiac intervals that contained one, two, three or four single-unit spikes were not different between the groups. Compared to the control group, HG elicited a larger increase in multi-unit total MSNA (Delta1002 +/- 50 compared with Delta636 +/- 76 units min(-1), P < 0.05) and single-unit MSNA spike incidence (Delta27 +/- 5 compared with Delta8 +/- 2 spikes (100 heart beats)(-1)), P < 0.01) in the CHF patients. More importantly, the percentage of cardiac intervals that contained two or three single-unit spikes was increased (P < 0.05) during exercise in the CHF group only (Delta8 +/- 2% and Delta5 +/- 1% for two and three spikes, respectively). These results suggest that the larger multi-unit total MSNA response observed during HG in CHF is brought about in part by an increase in the probability of multiple firing of single-unit sympathetic neurones.
authors.affiliation: Disease Control and Homeostasis, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan. sakurasoma1209@yahoo.co.jp
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Murai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takamura
authors.forename: Michirou
authors.initials: M
authors.lastname: Maruyama
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakano
authors.forename: Tatsunori
authors.initials: T
authors.lastname: Ikeda
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Kan-ichi
authors.initials: K
authors.lastname: Otowa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ootsuji
authors.forename: Masaki
authors.initials: M
authors.lastname: Okajima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Furusho
authors.forename: Shigeo
authors.initials: S
authors.lastname: Takata
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kaneko
mesh_terms: D000200:Action Potentials; D000368:Aged; D001794:Blood Pressure; D016022:Case-Control Studies; D002908:Chronic Disease; D015444:Exercise; D017079:Exercise Tolerance; D005260:Female; D018737:Hand Strength; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation*; D010543:Peroneal Nerve / Q000503:physiopathology; D011999:Recruitment, Neurophysiological; D012018:Reflex; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014661:Vasoconstriction