Baudoux S, Burrows M
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
J Exp Biol. 1998 Dec;201(Pt 24):3339-54. doi: 10.1242/jeb.201.24.3339.
The segmental ganglia of the locust contain efferent neuromodulatory neurones with cell bodies at the dorsal midline and axons that supply muscles and other tissue on both sides of the body. These are the dorsal unpaired median (DUM) neurones. Intracellular recordings were made from pairs of known metathoracic efferent DUM neurones in locusts in which all nerves were intact and in isolated metathoracic ganglia. The 19 metathoracic, efferent DUM neurones were identified according to the nerve roots through which their axons emerge from the ganglion. The synaptic potentials in these DUM neurones have been analysed to investigate how these neurones are activated and how their spikes are controlled. The degree of correlation between the synaptic potentials in particular pairs of neurones was quantified using a correlation analysis. This allowed the population of DUM neurones to be divided into three subsets that also map onto an anatomical grouping based on the distribution of their axons in the lateral nerves: (i) DUM1 neurones (DUMDL and DUM1b); (ii) DUM3 and DUM3,4 neurones; and (iii) DUM3,4,5, DUM5b neurones and DUMETi. Individual neurones within each subset showed strong correlations between their synaptic potentials, in both intact locusts and isolated ganglia, and tended to spike at the same time. Neurones in different subsets had few synaptic potentials in common and tended to spike independently. The persistence of common synaptic potentials in neurones of the three subsets in isolated ganglia indicates that they are derived from neurones within the metathoracic ganglion. The DUM neurones that had many common synaptic potentials in a quiescent locust responded in similar ways to mechanosensory stimulation of different parts of the body. DUM3,4, 5 and DUM5 neurones gave the clearest and most consistent responses to stimulation of mechanoreceptors on either hind leg. DUM3 and DUM3, 4 neurones responded variably, but usually with a hyperpolarisation. DUM1 neurones were rarely excited by mechanosensory stimuli but, like the preceding group, their responses were dependent upon whether the locust was moving its legs. These results lend further support to the idea that there is a subdivision of action amongst this population of DUM neurones, with those supplying the same targets being driven by the same presynaptic local neurones.
蝗虫的节段神经节包含传出性神经调节神经元，其细胞体位于背中线，轴突为身体两侧的肌肉和其他组织提供支配。这些就是背侧不成对中间神经元（DUM神经元）。在神经均完整的蝗虫以及分离的后胸神经节中，对已知的后胸传出性DUM神经元对进行了细胞内记录。根据其轴突从神经节发出所经过的神经根，鉴定出了19个后胸传出性DUM神经元。对这些DUM神经元中的突触电位进行了分析，以研究这些神经元是如何被激活的以及它们的动作电位是如何被控制的。使用相关性分析对特定神经元对之间的突触电位的相关程度进行了量化。这使得DUM神经元群体可以被分为三个子集，这三个子集也对应基于其轴突在侧神经中的分布的一种解剖学分组：（i）DUM1神经元（DUMDL和DUM1b）；（ii）DUM3和DUM3,4神经元；以及（iii）DUM3,4,5、DUM5b神经元和DUMETi。每个子集中的单个神经元在完整蝗虫和分离神经节中，其突触电位之间都表现出很强的相关性，并且倾向于同时产生动作电位。不同子集中的神经元很少有共同的突触电位，并且倾向于独立产生动作电位。在分离神经节中，三个子集中的神经元中共同突触电位的持续存在表明它们源自后胸神经节内的神经元。在静止蝗虫中具有许多共同突触电位的DUM神经元，对身体不同部位的机械感觉刺激有相似的反应方式。DUM3,4、5和DUM5神经元对任一后腿上机械感受器的刺激给出了最清晰、最一致的反应。DUM3和DUM3,4神经元的反应各不相同，但通常是超极化反应。DUM1神经元很少被机械感觉刺激所兴奋，但与前一组一样，它们的反应取决于蝗虫是否在移动其腿部。这些结果进一步支持了这样一种观点，即在这群DUM神经元中存在功能细分，那些支配相同靶标的神经元由相同的突触前局部神经元驱动。
