Paired associative stimulation induces change in presynaptic inhibition of Ia terminals in wrist flexors in humans.
Paired associative stimulation induces change in presynaptic inhibition of Ia terminals in wrist flexors in humans.
复制标题
成对的联想刺激会引起人类腕屈肌 Ia 末端突触前抑制的变化。
DOI：
10.1152/jn.00761.2009
复制
发表时间：
2010
影响因子：
2.5
通讯作者：
Hallett,Mark
中科院分区：
文献类型：
--
作者：
Lamy,Jean-Charles;Russmann,Heike;Shamim,EjazA;Meunier,Sabine;Hallett,Mark
在清醒的人类中，通过对运动皮质的配对联想刺激(PAS)，可以诱导皮质脊髓对肌肉投射强度的增强。尽管大多数先前的研究支持PAS增加运动诱发电位(MEP)的幅度涉及皮质突触的长时程增强(LTP)样机制的假说，但已有报道PAS后脊髓兴奋性的变化，提示皮质和脊髓的兴奋性平行改变。在第一系列实验(实验1)中，我们证实了PAS对腕屈肌(FCR)MEPs和FCRH反射募集曲线均有增强作用。为了阐明导致H反射幅度变化的机制，我们用相同的受试者检验了一种假设，即H反射的增强是由控制Ia传入放电的机制的有效性下调引起的，包括突触前Ia抑制和激活后抑制。为了解决这个问题，测定了PAS前后FCRIa终末突触前Ia抑制(D1和D2抑制法；实验2)和激活后抑制(实验3)的量。结果表明，PAS可显著降低FCR终末的突触前Ia抑制，并伴有H反射的易化。激活后抑郁不受PAS的影响。PAS对节段性兴奋的增强依赖于PAS对控制突触前抑制的中间神经元的选择性作用。
Enhancements in the strength of corticospinal projections to muscles are induced in conscious humans by paired associative stimulation (PAS) to the motor cortex. Although most of the previous studies support the hypothesis that the increase of the amplitude of motor evoked potentials (MEPs) by PAS involves long-term potentiation (LTP)-like mechanism in cortical synapses, changes in spinal excitability after PAS have been reported, suggestive of parallel modifications in both cortical and spinal excitability. In a first series of experiments (experiment 1), we confirmed that both flexor carpi radialis (FCR) MEPs and FCR H reflex recruitment curves are enhanced by PAS. To elucidate the mechanism responsible for this change in the H reflex amplitude, we tested, using the same subjects, the hypothesis that enhanced H reflexes are caused by a down-regulation of the efficacy of mechanisms controlling Ia afferent discharge, including presynaptic Ia inhibition and postactivation depression. To address this question, amounts of both presynaptic Ia inhibition of FCR Ia terminals (D1and D2 inhibitions methods;experiment 2) and postactivation depression (experiment 3) were determined before and after PAS. Results showed that PAS induces a significant decrease of presynaptic Ia inhibition of FCR terminals, which was concomitant with the facilitation of the H reflex. Postactivation depression was unaffected by PAS. It is argued that enhancement of segmental excitation by PAS relies on a selective effect of PAS on the interneurons controlling presynaptic inhibition of Ia terminals.