Kitazawa S, Ohki Y, Sasaki M, Xi M, Hongo T
Department of Neurophysiology, Faculty of Medicine, University of Tokyo, Japan.
Exp Brain Res. 1993;95(2):291-307. doi: 10.1007/BF00229787.
This study explored the locations and input-output properties of a large population of putative premotor neurones of skin reflex pathways in the cat. These neurones, interneurones excited by forelimb skin afferents and antidromically from the T1 motor nucleus (MN) and/or the lateral funiculus (LF, C8/T1 border), termed antidromic cells, were extracellularly recorded at C6-8. Selection of this site was based on data showing that cells retrogradely HRP labelled from the T1 MN were most numerous in C6-8 and the observation that transection of LF at the C8/T1 border abolished most skin-evoked postsynaptic potentials of T1 motoneurones. Antidromic cells were located in laminae IV-V, VI and VII. The latencies of antidromic excitation ranged from 0.4 to 1.8 ms, with a tendency for laminae IV-V cells to show longer latencies than laminae VI and VII cells. Latency of skin-evoked excitation ranged from 0.6 ms (IV-V cells), 0.8 ms (VI) and 1.4 ms (VII) to greater than 5 ms. The sum of the ortho- and antidromic latencies (estimated central latency) of individual cells explained the central latencies of skin-evoked postsynaptic potentials in T1 motoneurones. Skin-evoked firing responses (average of eight to ten cells) were earliest and largest in laminae IV-V antidromic cells, and latest and smallest in lamina VII cells. The antidromic cells who received inputs from muscle afferents and descending tracts. The following three results support the suggestion that the sampled antidromic cells are mostly premotor neurones. (1) Projection to the T1 MN via LF was verified in six laminae IV-VII antidromic cells, as tested with threshold mapping for antidromic excitation. (2) Three skin-excited axons of the middle LF projected to T1 MN, as revealed by intra-axonal staining (HRP). (3) PHA-L injection in laminae I-V of C8 anterogradely labelled terminals in lamina IX and LF axons at T1. It is suggested that last-order neurones of skin reflex pathways to T1 motoneurones are widely distributed in laminae IV-VII of C6-8 and consist of a variety of neurones with different locations and input patterns.
本研究探讨了猫皮肤反射通路中大量假定的运动前神经元的位置和输入-输出特性。这些神经元为中间神经元，可被前肢皮肤传入神经兴奋，并可从T1运动核（MN）和/或外侧索（LF，C8/T1边界）逆向兴奋，称为逆向细胞，在C6-8水平进行了细胞外记录。选择该部位是基于以下数据：从T1运动核逆向HRP标记的细胞在C6-8水平数量最多，以及观察到在C8/T1边界切断外侧索可消除T1运动神经元的大多数皮肤诱发的突触后电位。逆向细胞位于IV-V层、VI层和VII层。逆向兴奋的潜伏期为0.4至1.8毫秒，IV-V层细胞的潜伏期往往比VI层和VII层细胞更长。皮肤诱发兴奋的潜伏期范围为0.6毫秒（IV-V层细胞）、0.8毫秒（VI层）和1.4毫秒（VII层）至大于5毫秒。单个细胞的正向和逆向潜伏期之和（估计的中枢潜伏期）解释了T1运动神经元中皮肤诱发的突触后电位的中枢潜伏期。皮肤诱发的放电反应（8至10个细胞的平均值）在IV-V层逆向细胞中最早且最大，在VII层细胞中最晚且最小。逆向细胞接受来自肌肉传入神经和下行传导束的输入。以下三个结果支持所采样的逆向细胞大多为运动前神经元这一观点。（1）通过逆向兴奋阈值映射测试，在6个IV-VII层逆向细胞中证实了通过外侧索向T1运动核的投射。（2）轴突内染色（HRP）显示，中间外侧索的3条皮肤兴奋轴突投射到T1运动核。（3）在C8的I-V层注射PHA-L，顺行标记了IX层的终末和T1处的外侧索轴突。提示T1运动神经元皮肤反射通路的最后一级神经元广泛分布于C6-8的IV-VII层，由具有不同位置和输入模式的多种神经元组成。
