Department of Neuroscience, Karolinska Institutet, Stockholm SE 17177, Sweden.
Neuroscience. 2009 Dec 15;164(3):1057-67. doi: 10.1016/j.neuroscience.2009.08.069. Epub 2009 Sep 6.
The fundamental network for locomotion in all vertebrates contains a central pattern generator or CPG that produces the required motor output in the spinal cord. In the lamprey spinal cord different classes of interneuron's forming the core CPG circuitry have been characterized based on their morphological and electrophysiological features. The commissural interneuron's (C-INs) represent one essential component of CPG that have been implicated in controlling left-right alternation of the motor activity during swimming. However, it is still unclear if the C-INs displays a homogenous neurotransmitter phenotype and how they are distributed. In this paper we investigated the segmental distribution of glycine, glutamate and GABA-immunoreactive (ir) C-INs by combining retrograde Neurobiotin tracing with specific antibodies for these transmitters. The C-INs were more abundant in caudal and rostral segments adjacent to the injection site and their number gradually decreased in more distal segments, suggesting that these interneurons project over a short distance. The glycine-ir neurons represented around 50% of the total C-INs, while glutamate-ir neurons represented only 29%. Both types of C-INs were homogenously distributed over different segments along the spinal cord. Finally, no Neurobiotin labeled C-INs displayed GABA-ir, although many interneurons were ir to GABA, suggesting that GABAergic interneurons are not directly responsible for controlling left-right alternation of activity during locomotion in lamprey. Overall, these results show that the C-INs display a gradual rostrocaudal distribution and consist of both glycine- and glutamate-ir neurons. The difference in the proportion of inhibitory and excitatory C-INs represents an anatomical substrate that can ensure the predominance of alternating activity during locomotion.
所有脊椎动物的基本运动网络都包含一个中枢模式发生器（CPG），它在脊髓中产生所需的运动输出。在七鳃鳗的脊髓中，根据其形态和电生理特征，已经对构成核心 CPG 电路的不同类别的中间神经元进行了描述。联络中间神经元（C-INs）是 CPG 的一个重要组成部分，它们被认为在控制游泳时的左右交替运动活动中起作用。然而，目前尚不清楚 C-INs 是否表现出同质的神经递质表型，以及它们是如何分布的。在本文中，我们通过将逆行神经生物素示踪与这些递质的特异性抗体相结合，研究了甘氨酸、谷氨酸和 GABA 免疫反应性（ir）C-INs 的节段分布。C-INs 在靠近注射部位的尾部和头部节段更为丰富，并且在更远的节段数量逐渐减少，这表明这些中间神经元的投射距离较短。甘氨酸 ir 神经元约占总 C-INs 的 50%，而谷氨酸 ir 神经元仅占 29%。这两种类型的 C-INs 在脊髓的不同节段上均匀分布。最后，没有被神经生物素标记的 C-INs 显示 GABA-ir，尽管许多中间神经元对 GABA 呈 ir 反应，这表明 GABA 能中间神经元不是直接负责控制七鳃鳗运动时左右交替活动的。总的来说，这些结果表明 C-INs 呈逐渐的头尾部分布，由甘氨酸和谷氨酸 ir 神经元组成。抑制性和兴奋性 C-INs 的比例差异代表了一种解剖学基础，可确保运动时交替活动的主导地位。
