Sensory information arising from limb movements controls the spinal locomotor circuitry to adapt the motor pattern to demands of the environment. Stimulation of extensor group (gr) I afferents during fictive locomotion in decerebrate cats prolongs the ongoing extension, and terminates ongoing flexion with an initiation of the subsequent extension, i. e. “resetting to extension”. Moreover, instead of the classical Ib non-reciprocal inhibition, stimulation of extensor gr I afferents produces a polysynaptic excitation in extensor motoneurons with latencies (∼3.5 – 4.0 ms) compatible with 3 interposed interneurons. We assume that some interneurons in this pathway actually belong to the rhythm-generating layer of the locomotor Central Pattern Generator (CPG), since their activity was correlated to a resetting of the rhythm. In the present work fictive locomotion was (mostly) induced by i.v. injection of nialamide followed by L-DOPA in paralyzed cats following decerebration and spinalization at C1 level. In some experiments, we extended previous observations during fictive locomotion on the emergence and locomotor state-dependence of polysynaptic excitatory postsynaptic potentials from extensor gr I afferents to ankle extensor motoneurons. However, the main focus was to record location and properties of interneurons (n=62) that i) were active during the extensor phase of fictive locomotion and ii) received short-latency excitation (mono-, di- or polysynaptic) from extensor gr I afferents. We conclude that the interneurons recorded fulfill the characteristics to belong to the neuronal pathway activated by extensor gr I afferents during locomotion, and may contribute to the ‘resetting to extension’ as part of the locomotor CPG.

由肢体运动产生的感觉信息控制脊柱运动电路，以使运动模式适应环境需求。去脑猫的虚构运动中对伸肌群（gr）I的刺激延长了进行中的伸展，并终止了进行中的屈曲，并随后开始伸展，即“复位为伸展”。此外，代替经典的Ib非对等抑制，对伸肌gr I传入神经的刺激在伸肌运动神经元中产生了与3个插入的中间神经元兼容的潜伏期（〜3.5 – 4.0 ms）的多突触兴奋。我们假设此路径中的某些中间神经实际上属于运动中央模式发生器（CPG）的节奏产生层，因为它们的活动与节奏的恢复相关。在目前的工作中，虚构的运动（主要）是在瘫痪的猫在C1水平进行小脑脊柱化后，静脉注射烟酰胺和L-DOPA诱导的。在一些实验中，我们将以前的观察扩展到虚拟运动过程中，从伸肌gr I传入脚踝伸肌运动神经元的多突触兴奋性突触后突触电位的出现和运动状态依赖性。然而，主要的重点是记录中间神经元的位置和性质（n = 62），即i）在虚构运动的伸肌阶段处于活动状态，并且ii）从伸肌gr获得短时延激发（单突触，双突触或多突触）。我来了 我们得出的结论是，记录的中间神经元具有在运动过程中属于伸肌gr I传入激活的神经元通路的特征，