Zhang W, Pombal M A, el Manira A, Grillner S
Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
J Comp Neurol. 1996 Oct 14;374(2):278-90. doi: 10.1002/(SICI)1096-9861(19961014)374:2<278::AID-CNE9>3.0.CO;2-#.
5-hydroxytryptamine (5-HT) is known to modulate the locomotion generator network in the lamprey spinal cord, but little is known about the pattern of 5-HT innervation along the spinal cord. The distribution of 5-HT-immunoreactive (5-HT-ir) cells and fibers, as well as the effects of 5-HT on the locomotor network in the rostral and caudal parts of the spinal cord were compared in two lamprey species, Lampetra fluviatilis and Petromyzon marinus. Intraspinal 5-HT cells form a very dense ventromedial plexus in which the dendrites of neurons forming the locomotor network are distributed. The number of 5-HT cells and varicosities in this plexus decreases in the fin area (segments 70-90), and then increases somewhat in the most caudal segments. The descending 5-HT fibers from the rhombencephalon are located in the lateral and ventral columns, and their numbers gradually decrease to around 50% in the tail part of the spinal cord. In contrast, the number of 5-HT-ir axons in the dorsal column remains the same along the spinal cord. Bath application of both N-methyl-D-aspartic acid (NMDA, 20-250 microM) and D-glutamate (250-1000 microM) was used to induce fictive locomotion in the isolated spinal cord. Bath application of 5-HT (1 microM) reduced the burst frequency in the presence of NMDA. The 5-HT effect was, however, significantly greater in the rostral as compared to the caudal part. With D-glutamate, the 5-HT effects was instead more pronounced in the caudal spinal cord. To account for this difference in 5-HT effects on NMDA- and D-glutamate-induced fictive locomotion, the cellular effect of D-glutamate was further investigated. It activates not only NMDA, but also alpha amino-3-hydroxy-5-methyl-4-isoxyl propionate (AMPA)/kainate and metabotropic glutamate receptors. In contrast to NMDA, D-glutamate did not elicit tetrodotoxin (TTX)-resistant membrane potential oscillations. This difference in action between NMDA (selective NMDA receptor agonist) and D-glutamate (mixed agonist) may partially account for the differences in effect of 5-HT on the locomotor pattern.
已知5-羟色胺（5-HT）可调节七鳃鳗脊髓中的运动发生器网络，但沿脊髓的5-HT神经支配模式却鲜为人知。在两种七鳃鳗，即河七鳃鳗和海七鳃鳗中，比较了5-HT免疫反应性（5-HT-ir）细胞和纤维的分布，以及5-HT对脊髓头端和尾端运动网络的影响。脊髓内的5-HT细胞形成一个非常密集的腹内侧丛，构成运动网络的神经元树突分布于此丛中。该丛中5-HT细胞和曲张体的数量在鳍区（第70 - 90节段）减少，然后在最尾端节段有所增加。来自菱脑的下行5-HT纤维位于外侧柱和腹侧柱，其数量在脊髓尾部逐渐减少至约50%。相比之下，背侧柱中5-HT-ir轴突的数量沿脊髓保持不变。在离体脊髓中，通过浴槽给药N-甲基-D-天冬氨酸（NMDA，20 - 250微摩尔）和D-谷氨酸（250 - 1000微摩尔）来诱导虚拟运动。在存在NMDA的情况下，浴槽给药5-HT（1微摩尔）可降低爆发频率。然而，与尾端部分相比，5-HT在头端的作用明显更大。对于D-谷氨酸，5-HT的作用在尾端脊髓中反而更明显。为了解释5-HT对NMDA和D-谷氨酸诱导的虚拟运动作用的这种差异，进一步研究了D-谷氨酸的细胞效应。它不仅激活NMDA，还激活α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）/海人藻酸受体和代谢型谷氨酸受体。与NMDA不同，D-谷氨酸不会引发对河豚毒素（TTX）有抗性的膜电位振荡。NMDA（选择性NMDA受体激动剂）和D-谷氨酸（混合激动剂）之间的这种作用差异可能部分解释了5-HT对运动模式作用的差异。
