Survival for vertebrate animals is dependent on the ability to successfully find food, locate a mate, and avoid predation. Each of these behaviors requires motor control, which is set by a combination of kinematic properties. For example, the frequency and amplitude of motor output combine in a multiplicative manner to determine features of locomotion such as distance traveled, speed, force (thrust), and vigor. Although there is a good understanding of how different populations of excitatory spinal interneurons establish locomotor frequency, there is a less thorough mechanistic understanding for how locomotor amplitude is established. Recent evidence indicates that locomotor amplitude is regulated in part by a subset of functionally and morphologically distinct V2a excitatory spinal interneurons (type II, non-bursting) in larval and adult zebrafish. Here we provide direct evidence, for the first time, that most V3 interneurons (V3-INs), which are a developmentally and genetically defined population of ventromedial glutamatergic spinal neurons, are active during fictive swimming. We also show that elimination of the spinal V3-IN population reduces the proportion of active MNs during fictive swimming but does not alter the range of locomotor frequencies produced. These data are consistent with V3-INs providing excitatory drive to spinal motor neurons and contributing to the production of locomotor amplitude, but not frequency, during swimming in larval zebrafish.

中文翻译：

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V3中间神经元在斑马鱼幼虫体内虚拟游泳期间活跃并招募脊髓运动神经元

脊椎动物的生存取决于成功寻找食物、找到配偶和避免捕食的能力。这些行为中的每一个都需要运动控制，这是由运动学属性的组合设置的。例如，电机输出的频率和幅度以乘法方式组合以确定运动特征，例如行进距离、速度、力（推力）和活力。尽管对兴奋性脊髓中间神经元的不同群体如何建立运动频率有很好的理解，但对如何建立运动幅度的机制理解不那么透彻。最近的证据表明，运动幅度部分受功能和形态上不同的 V2a 兴奋性脊髓中间神经元的子集（II 型，非爆裂）在幼虫和成年斑马鱼中。在这里，我们首次提供了直接证据，表明大多数 V3 中间神经元 (V3-INs) 是发育和遗传定义的腹内侧谷氨酸能脊髓神经元群，在虚构游泳期间活跃。我们还表明，消除脊髓 V3-IN 人口减少了虚构游泳期间活跃 MN 的比例，但不会改变产生的运动频率范围。这些数据与 V3-IN 一致，它为脊髓运动神经元提供兴奋性驱动，并有助于在幼虫斑马鱼游泳期间产生运动幅度，但不是频率。它们是发育和遗传定义的腹内侧谷氨酸能脊髓神经元群，在虚构的游泳过程中活跃。我们还表明，消除脊髓 V3-IN 人口减少了虚构游泳期间活跃 MN 的比例，但不会改变产生的运动频率范围。这些数据与 V3-IN 一致，它为脊髓运动神经元提供兴奋性驱动，并有助于在幼虫斑马鱼游泳期间产生运动幅度，但不是频率。它们是发育和遗传定义的腹内侧谷氨酸能脊髓神经元群，在虚构的游泳过程中活跃。我们还表明，消除脊髓 V3-IN 人口减少了虚构游泳期间活跃 MN 的比例，但不会改变产生的运动频率范围。这些数据与 V3-IN 一致，它为脊髓运动神经元提供兴奋性驱动，并有助于在幼虫斑马鱼游泳期间产生运动幅度，但不是频率。