Sorbonne Université, Paris Brain Institute (Institut du Cerveau, ICM), Institut National de la Santé et de la Recherche Médicale U1127, Centre National de la Recherche Scientifique Unité Mixte de Recherche 7225, Assistance Publique-Hôpitaux de Paris, Campus Hospitalier Pitié-Salpêtrière, Paris, France.
Institut Langevin, École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, Paris Sciences et Lettres, Centre National de la Recherche Scientifique, Paris, France.
Nat Neurosci. 2023 Oct;26(10):1775-1790. doi: 10.1038/s41593-023-01418-0. Epub 2023 Sep 4.
The mesencephalic locomotor region (MLR) is a brain stem area whose stimulation triggers graded forward locomotion. How MLR neurons recruit downstream vsx2 (V2a) reticulospinal neurons (RSNs) is poorly understood. Here, to overcome this challenge, we uncovered the locus of MLR in transparent larval zebrafish and show that the MLR locus is distinct from the nucleus of the medial longitudinal fasciculus. MLR stimulations reliably elicit forward locomotion of controlled duration and frequency. MLR neurons recruit V2a RSNs via projections onto somata in pontine and retropontine areas, and onto dendrites in the medulla. High-speed volumetric imaging of neuronal activity reveals that strongly MLR-coupled RSNs are active for steering or forward swimming, whereas weakly MLR-coupled medullary RSNs encode the duration and frequency of the forward component. Our study demonstrates how MLR neurons recruit specific V2a RSNs to control the kinematics of forward locomotion and suggests conservation of the motor functions of V2a RSNs across vertebrates.
中脑运动区（MLR）是脑干部位的一个区域，刺激该区域会引发逐渐增强的前进运动。但是，我们对于 MLR 神经元如何招募下游 vsx2（V2a）网状脊髓神经元（RSNs）的机制知之甚少。为了克服这一挑战，我们在透明的幼鱼斑马鱼中揭示了 MLR 的位置，并表明 MLR 位置与内侧纵束核不同。MLR 刺激可靠地引发具有可控持续时间和频率的前进运动。MLR 神经元通过投射到桥脑和桥后区域的体部以及延髓的树突上，招募 V2a RSN。对神经元活动的高速体积成像显示，与 MLR 紧密结合的 RSNs 在转向或向前游泳时活跃，而与 MLR 弱结合的延髓 RSN 则编码向前运动的持续时间和频率。我们的研究表明了 MLR 神经元如何招募特定的 V2a RSN 来控制前进运动的运动学，并表明 V2a RSN 的运动功能在脊椎动物中是保守的。
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