Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden.
J Comp Neurol. 2013 Nov;521(16):3847-62. doi: 10.1002/cne.23382.
In lampreys, stretch receptor neurons (SRNs) are located at the margins of the spinal cord and activated by longitudinal stretch in that area caused by body bending. The aim of this study was a comprehensive analysis of motor responses to bending of the lamprey body in different planes and at different rostrocaudal levels. For this purpose, in vitro preparation of the spinal cord isolated together with notochord was used, and responses to bending were recorded from SRNs, as well as from motoneurons innervating the dorsal (dMNs) and ventral (vMNs) parts of a myotome. It was found that SRNs were activated on the convex (stretched) side of the preparation during bending both in the yaw and in the pitch plane. By contrast, responses of motoneurons depended on the site and plane of bending. In the yaw plane, concave responses to bending of rostral segments and convex responses to bending of mid-body segments prevailed. In the pitch plane, convex responses in dMNs and concave responses in vMNs to bending in mid-body segments prevailed. These spinal reflexes could contribute to feedback regulation of locomotor body undulations and to the control of body configuration during locomotion. After a longitudinal split of the spinal cord, only convex responses in motoneurons were present, suggesting an important role of contralateral networks in determining the type of motor response. Stimulation of the brainstem changed the type of motor response to bending, suggesting that these spinal reflexes can be modified by supraspinal signals in accordance with different motor behaviors.
在七鳃鳗中，伸展感受器神经元 (SRN) 位于脊髓边缘，由身体弯曲引起的该区域的纵向伸展激活。本研究的目的是全面分析七鳃鳗身体在不同平面和不同头尾水平弯曲的运动反应。为此，使用了与脊索一起分离的脊髓体外制备，并从 SRN 以及支配肌节背侧 (dMNs) 和腹侧 (vMNs) 部分的运动神经元记录到对弯曲的反应。结果发现，在 yaw 和 pitch 平面弯曲时，SRN 在制备物的凸侧（伸展侧）被激活。相比之下，运动神经元的反应取决于弯曲的部位和平面。在 yaw 平面中，弯曲的前体段的凹侧反应和弯曲的中体段的凸侧反应占主导地位。在 pitch 平面中，弯曲的中体段的 dMNs 的凸侧反应和 vMNs 的凹侧反应占主导地位。这些脊髓反射可能有助于运动身体波动的反馈调节，并有助于运动过程中身体形态的控制。脊髓纵向分裂后，只有运动神经元存在凸侧反应，表明对侧网络在确定运动反应类型方面起着重要作用。脑干刺激改变了弯曲的运动反应类型，表明这些脊髓反射可以根据不同的运动行为被来自上位中枢的信号进行修饰。
