Ménard A, Leblond H, Gossard J P
Centre de Recherche en Sciences Neurologiques, Département de Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada, H3C 3J7.
J Neurosci. 1999 Jan 1;19(1):391-400. doi: 10.1523/JNEUROSCI.19-01-00391.1999.
The aim of this study is to understand the functional organization of presynaptic inhibition in muscle primary afferents during locomotion. Primary afferent depolarization (PAD) associated with presynaptic inhibition was recorded intra-axonally in identified afferents from various hindlimb muscles in L6-L7 spinal segments during fictive locomotion in the decerebrate cat. PADs were evoked by the stimulation of peripheral muscle nerves and were averaged in the different epochs of the fictive step cycle. Fifty-three trials recorded from 39 muscle axons (37 from group I and two from group II) were retained for analysis. The results showed that there was a significant phase-dependent modulation of PAD amplitude (p < 0.05) in a majority of muscle afferents (30 of 39, 77%). However, not all stimulated nerves led to significantly modulated PADs in a given axon (36 of 53 trials, 68%). We also observed that the pattern of modulation (phase for maximum and minimum PAD amplitude and the depth of modulation) varied with each recorded afferent, as well as with each stimulated nerve. We further evaluated the effect of PAD modulation on the phasic transmission of the monosynaptic reflex (MSR) and found that PADs decreased the MSR amplitude in all phases of the fictive step cycle, independent of the PAD pattern in individual group I fibers. We conclude that (1) PAD modulation patterns of all group I fibers contacting motoneurons led to an overall reduction in monosynaptic transmission, and (2) individual PAD patterns could participate in the control of transmission in specific reflex pathways during locomotion.
本研究的目的是了解运动过程中肌肉初级传入纤维突触前抑制的功能组织。在去大脑猫的虚拟运动期间，从L6-L7脊髓节段的各种后肢肌肉中，在已识别的传入纤维的轴突内记录与突触前抑制相关的初级传入纤维去极化（PAD）。通过刺激外周肌肉神经诱发PAD，并在虚拟步周期的不同阶段进行平均。保留了从39条肌肉轴突记录的53次试验（I组37条，II组2条）用于分析。结果表明，大多数肌肉传入纤维（39条中的30条，77%）的PAD振幅存在显著的相位依赖性调制（p<0.05）。然而，并非所有受刺激的神经在给定轴突中都能导致PAD的显著调制（53次试验中的36次，68%）。我们还观察到，调制模式（PAD最大和最小振幅的相位以及调制深度）随每条记录的传入纤维以及每条受刺激的神经而变化。我们进一步评估了PAD调制对单突触反射（MSR）相位传递的影响，发现PAD在虚拟步周期的所有阶段均降低了MSR振幅，与I组单个纤维中的PAD模式无关。我们得出结论：（1）所有与运动神经元接触的I组纤维的PAD调制模式导致单突触传递总体减少；（2）个体PAD模式可参与运动过程中特定反射通路的传递控制。
