Julian Colard, Marc Jubeau, Marion Crouzier, Julien Duclay, Thomas Cattagni
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We recorded conditioned or nonconditioned soleus Hoffmann (H) reflex with electromyography (EMG) to estimate the effectiveness of activated Ia afferents to discharge α-motoneurons, HPAD, PAD, and HF during passive shortening, static, and lengthening muscle conditions at short, intermediate, and long lengths. Our results show that the decrease of effectiveness of activated Ia afferents to discharge α-motoneurons and increase of postactivation depression during passive muscle lengthening occur at all muscle lengths. For PAD and HF, we found that longer muscle length increases the magnitude of regulation related to muscle lengthening. To conclude, our findings support an inhibitory effect (resulting from increased postactivation depression) of muscle lengthening and longer muscle length on the effectiveness of activated Ia afferents to discharge α-motoneurons. The increase in postactivation depression associated with muscle lengthening can be attributed to the amplification of Ia afferents discharge.<b>NEW & NOTEWORTHY</b> Original results are that in response to passive muscle lengthening and increased muscle length, inhibition of the effectiveness of activated Ia afferents to discharge α-motoneurons increases, with primary afferent depolarization and homosynaptic postactivation depression mechanisms playing central roles in this regulatory process. Our findings highlight for the first time a cumulative inhibitory effect of muscle lengthening and increased muscle length on the effectiveness of activated Ia afferents to discharge α-motoneurons.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":null,"pages":null},"PeriodicalIF":2.1000,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Effect of muscle length on the modulation of H-reflex and inhibitory mechanisms of Ia afferent discharges during passive muscle lengthening.\",\"authors\":\"Julian Colard, Marc Jubeau, Marion Crouzier, Julien Duclay, Thomas Cattagni\",\"doi\":\"10.1152/jn.00142.2024\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>The effectiveness of activated Ia afferents to discharge α-motoneurons is decreased during passive muscle lengthening compared with static and shortening muscle conditions. Evidence suggests that these regulations are explained by <i>1</i>) greater postactivation depression induced by homosynaptic postactivation depression (HPAD) and <i>2</i>) primary afferent depolarization (PAD). It remains uncertain whether muscle length impacts the muscle lengthening-related aspect of regulation of the effectiveness of activated Ia afferents to discharge α-motoneurons, HPAD, PAD, and heteronymous Ia facilitation (HF). We conducted a study involving 15 healthy young individuals. We recorded conditioned or nonconditioned soleus Hoffmann (H) reflex with electromyography (EMG) to estimate the effectiveness of activated Ia afferents to discharge α-motoneurons, HPAD, PAD, and HF during passive shortening, static, and lengthening muscle conditions at short, intermediate, and long lengths. 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引用次数: 0
摘要
与静态和肌肉缩短条件相比,被动肌肉拉长时激活的 Ia 传入神经释放ᵯC-肌突触的有效性降低。有证据表明,这些调节的原因是:(1)同突触激活后抑制(HPAD)和(2)初级传入去极化(PAD)引起的更大的激活后抑制。目前仍不确定肌肉长度是否会影响激活的 Ia 传入器对ᵯC-运动神经元放电的有效性、HPAD、PAD 和异名 Ia 促进(HF)的调节中与肌肉拉长相关的方面。我们进行了一项涉及 15 名健康年轻人的研究。我们用肌电图(EMG)记录了条件性或非条件性比目鱼肌霍夫曼(H)反射,以估计在被动拉长、缩短和静止肌肉短、中、长时,激活的 Ia 传入对ᵯC-肌突元、HPAD、PAD 和 HF 的放电有效性。我们的研究结果表明,在被动肌肉拉长过程中,激活的 Ia 传入神经释放ᵯC-肌突触的有效性降低,激活后抑制增加,这发生在所有肌肉长度上。对于 PAD 和 HF,我们发现肌肉长度越长,与肌肉拉长相关的调节幅度就越大。总之,我们的研究结果表明,肌肉拉长和较长的肌肉长度对激活的 Ia 传入神经释放 α-肌突触的有效性有抑制作用(由激活后抑制增加引起)。与肌肉延长相关的激活后抑制的增加可归因于 Ia 传入器放电的放大。
Effect of muscle length on the modulation of H-reflex and inhibitory mechanisms of Ia afferent discharges during passive muscle lengthening.
The effectiveness of activated Ia afferents to discharge α-motoneurons is decreased during passive muscle lengthening compared with static and shortening muscle conditions. Evidence suggests that these regulations are explained by 1) greater postactivation depression induced by homosynaptic postactivation depression (HPAD) and 2) primary afferent depolarization (PAD). It remains uncertain whether muscle length impacts the muscle lengthening-related aspect of regulation of the effectiveness of activated Ia afferents to discharge α-motoneurons, HPAD, PAD, and heteronymous Ia facilitation (HF). We conducted a study involving 15 healthy young individuals. We recorded conditioned or nonconditioned soleus Hoffmann (H) reflex with electromyography (EMG) to estimate the effectiveness of activated Ia afferents to discharge α-motoneurons, HPAD, PAD, and HF during passive shortening, static, and lengthening muscle conditions at short, intermediate, and long lengths. Our results show that the decrease of effectiveness of activated Ia afferents to discharge α-motoneurons and increase of postactivation depression during passive muscle lengthening occur at all muscle lengths. For PAD and HF, we found that longer muscle length increases the magnitude of regulation related to muscle lengthening. To conclude, our findings support an inhibitory effect (resulting from increased postactivation depression) of muscle lengthening and longer muscle length on the effectiveness of activated Ia afferents to discharge α-motoneurons. The increase in postactivation depression associated with muscle lengthening can be attributed to the amplification of Ia afferents discharge.NEW & NOTEWORTHY Original results are that in response to passive muscle lengthening and increased muscle length, inhibition of the effectiveness of activated Ia afferents to discharge α-motoneurons increases, with primary afferent depolarization and homosynaptic postactivation depression mechanisms playing central roles in this regulatory process. Our findings highlight for the first time a cumulative inhibitory effect of muscle lengthening and increased muscle length on the effectiveness of activated Ia afferents to discharge α-motoneurons.
期刊介绍:
The Journal of Neurophysiology publishes original articles on the function of the nervous system. All levels of function are included, from the membrane and cell to systems and behavior. Experimental approaches include molecular neurobiology, cell culture and slice preparations, membrane physiology, developmental neurobiology, functional neuroanatomy, neurochemistry, neuropharmacology, systems electrophysiology, imaging and mapping techniques, and behavioral analysis. Experimental preparations may be invertebrate or vertebrate species, including humans. Theoretical studies are acceptable if they are tied closely to the interpretation of experimental data and elucidate principles of broad interest.