Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, Stockholm S-17177, Sweden.
Neuron. 2011 Sep 22;71(6):1071-84. doi: 10.1016/j.neuron.2011.07.011. Epub 2011 Sep 21.
Neural networks in the spinal cord control two basic features of locomotor movements: rhythm generation and pattern generation. Rhythm generation is generally considered to be dependent on glutamatergic excitatory neurons. Pattern generation involves neural circuits controlling left-right alternation, which has been described in great detail, and flexor-extensor alternation, which remains poorly understood. Here, we use a mouse model in which glutamatergic neurotransmission has been ablated in the locomotor region of the spinal cord. The isolated in vitro spinal cord from these mice produces locomotor-like activity-when stimulated with neuroactive substances-with prominent flexor-extensor alternation. Under these conditions, unlike in control mice, networks of inhibitory interneurons generate the rhythmic activity. In the absence of glutamatergic synaptic transmission, the flexor-extensor alternation appears to be generated by Ia inhibitory interneurons, which mediate reciprocal inhibition from muscle proprioceptors to antagonist motor neurons. Our study defines a minimal inhibitory network that is needed to produce flexor-extensor alternation during locomotion.
节律产生和模式产生。节律产生通常被认为依赖于谷氨酸能兴奋性神经元。模式产生涉及控制左右交替的神经网络，这已经被详细描述过了，而屈肌-伸肌交替仍然知之甚少。在这里，我们使用了一种在脊髓运动区中谷氨酸能神经传递被阻断的小鼠模型。从这些小鼠中分离出的体外脊髓在受到神经活性物质刺激时会产生类似运动的活动，并且具有明显的屈肌-伸肌交替。在这些条件下，与对照小鼠不同的是，抑制性中间神经元网络产生有节奏的活动。在没有谷氨酸能突触传递的情况下，屈肌-伸肌交替似乎是由 Ia 抑制性中间神经元产生的，它们介导来自肌肉本体感受器到拮抗运动神经元的交互抑制。我们的研究定义了一个最小的抑制性网络，它是在运动过程中产生屈肌-伸肌交替所必需的。
