Rostro-caudal coordination of spinal motor output is essential for locomotion. Most spinal interneurons project axons longitudinally to govern locomotor output, yet their connectivity along this axis remains unclear. In this study, we use larval zebrafish to map synaptic outputs of a major inhibitory population, V1 (Eng1⁺) neurons, which are implicated in dual sensory and motor functions. We find that V1 neurons exhibit long axons extending rostrally and exclusively ipsilaterally for an average of 6 spinal segments; however, they do not connect uniformly with their post-synaptic targets along the entire length of their axon. Locally, V1 neurons inhibit motor neurons (both fast and slow) and other premotor targets, including V2a, V2b, and commissural premotor neurons. In contrast, V1 neurons make robust long-range inhibitory contacts onto a dorsal horn sensory population, the commissural primary ascending neurons (CoPAs). In a computational model of the ipsilateral spinal network, we show that this pattern of short-range V1 inhibition to motor and premotor neurons underlies burst termination, which is critical for coordinated rostro-caudal propagation of the locomotor wave. We conclude that spinal network architecture in the longitudinal axis can vary dramatically, with differentially targeted local and distal connections, yielding important consequences for function.

脊柱运动输出的 Rostro-caudal 协调对于运动至关重要。大多数脊髓中间神经元纵向投射轴突以控制运动输出，但它们沿该轴的连接性仍不清楚。在这项研究中，我们使用幼虫斑马鱼来绘制主要抑制群体 V1 (Eng1 ⁺) 神经元，它们与双重感觉和运动功能有关。我们发现 V1 神经元表现出长轴突，平均有 6 个脊髓节段向头侧延伸且仅向同侧延伸。然而，它们在轴突的整个长度上并没有与突触后目标一致地连接。在局部，V1 神经元抑制运动神经元（快速和慢速）和其他运动前目标，包括 V2a、V2b 和连合前运动神经元。相比之下，V1 神经元对背角感觉群体，即连合初级上行神经元 (CoPA) 进行强大的远程抑制性接触。在同侧脊柱网络的计算模型中，我们表明这种对运动和前运动神经元的短程 V1 抑制模式是突发终止的基础，这对于运动波的协调的rostro-caudal传播至关重要。我们得出结论，纵轴上的脊柱网络结构可能会有很大差异，局部和远端连接的目标不同，对功能产生重要影响。