title: Evidence for centrally induced cholinergic vasodilatation in skeletal muscle during voluntary one-legged cycling and motor imagery in humans.
abstract: We have recently reported that central command contributes to increased blood flow in both noncontracting and contracting vastus lateralis (VL) muscles at the early period of voluntary one-legged cycling. The purpose of this study was to examine whether sympathetic cholinergic vasodilatation mediates the increases in blood flows of both muscles during one-legged exercise. Following intravenous administration of atropine (10 μg/kg), eight subjects performed voluntary 1-min one-legged cycling (at 35% of maximal voluntary effort) and mental imagery of the exercise. The relative concentrations of oxygenated- and deoxygenated-hemoglobin (Oxy- and Deoxy-Hb) in the bilateral VL were measured as an index of muscle tissue blood flow with near-infrared spectroscopy (NIRS). The Oxy-Hb in both noncontracting and contracting VL increased at the early period of one-legged cycling, whereas the Deoxy-Hb did not alter at that period. Atropine blunted (P < 0.05) the Oxy-Hb responses of both VL muscles but did not affect the Deoxy-Hb responses. The time course and magnitude of the atropine-sensitive component in the Oxy-Hb response were quite similar between the noncontracting and contracting VL muscles. With no changes in the Deoxy-Hb and hemodynamics, imagery of one-legged cycling induced the bilateral increases in the Oxy-Hb, which were completely abolished by atropine. In contrast, imagery of a circle (with no relation to exercise) did not alter the NIRS signals, irrespective of the presence or absence of atropine. It is concluded that central command evokes cholinergic vasodilatation equally in bilateral VL muscles during voluntary one-legged cycling and motor imagery.
authors.affiliation: Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ishii
authors.forename: Kanji
authors.initials: K
authors.lastname: Matsukawa
authors.forename: Nan
authors.initials: N
authors.lastname: Liang
authors.forename: Kana
authors.initials: K
authors.lastname: Endo
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Idesako
authors.forename: Hironobu
authors.initials: H
authors.lastname: Hamada
authors.forename: Kazumi
authors.initials: K
authors.lastname: Ueno
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kataoka
keywords: Central command; exercise hyperemia; near-infrared spectroscopy (NIRS); sympathetic cholinergic nerve