Yamanaka K, Yamamoto S, Nakazawa K, Yano H, Suzuki Y, Fukunaga T
Motor Dysfunction Division, National Rehabilitation Center for the Disabled, Saitama, Japan.
J Gravit Physiol. 1999 Jul;6(1):P157-8.
Maximal H-reflex amplitude (Hmax) compared with maximal M-response (Mmax) has been generally used to assess the efficacy of the monosynaptic transmission from Ia afferents to alpha motoneurons in spinal cord. In previous studies, it has been demonstrated that H-reflex in soleus muscle (SOL) is inhibited during free standing due to an increase in presynaptic inhibition of the Ia afferent terminals to SOL motoneurones (Katz et al. 1988, Koceja et al. 1993). Transcranial magnetic stimulation (TMS) of human motor cortex excites the corticospinal system monosynapticaly connecting to spinal alpha motoneurones. However, it is not clear whether or not the motor evoked potentials (MEPs) in SOL and tibialis anterior (TA) muscles induced by TMS are modulated during standing (Ackermann et al. 1991, Lavoie et al. 1995). Considering that postural control functions change with exposure to weightlessness, we supposed that the excitability of SOL and TA spinal motoneurons from Ia afferents and/or corticospinal tracts during free standing would change after long-term bed rest (BR). The aim of this study was to investigate the effect of BR on H-reflex and MEP in SOL and TA during free standing.
最大H反射幅度（Hmax）与最大M反应（Mmax）的比值通常用于评估脊髓中Ia传入神经至α运动神经元的单突触传递效率。在先前的研究中，已证实站立时比目鱼肌（SOL）的H反射受到抑制，这是由于Ia传入神经终末至SOL运动神经元的突触前抑制增强所致（Katz等人，1988年；Koceja等人，1993年）。对人类运动皮层进行经颅磁刺激（TMS）可单突触激发皮质脊髓系统与脊髓α运动神经元相连。然而，尚不清楚站立期间TMS诱发的SOL和胫前肌（TA）肌肉中的运动诱发电位（MEP）是否受到调制（Ackermann等人，1991年；Lavoie等人，1995年）。考虑到姿势控制功能会随着失重状态而改变，我们推测长期卧床休息（BR）后，站立时来自Ia传入神经和/或皮质脊髓束的SOL和TA脊髓运动神经元的兴奋性会发生变化。本研究的目的是探讨BR对站立时SOL和TA的H反射和MEP的影响。
