Bicker G, Schäfer S, Ottersen O P, Storm-Mathisen J
Institut für Tierphysiologie-Neurobiologie, Freien Universität Berlin, FRG.
J Neurosci. 1988 Jun;8(6):2108-22. doi: 10.1523/JNEUROSCI.08-06-02108.1988.
Glutamate is considered to be the most likely transmitter candidate at excitatory synapses onto skeletal muscles of insects. We investigated the distribution of glutamate-like immunoreactivity (Glu-LI) in identified motor neurons of glutaraldehyde-fixed metathoracic ganglia of the locust in paraffin serial sections. The presumably glutamatergic fast and slow extensor tibiae motor neurons show Glu-LI, whereas other cells, including the GABAergic common inhibitory motor neurons and the cluster of octopaminergic dorsal unpaired median cells, show rather low levels of staining. Immunoreactivity of the fast extensor tibiae motor neuron is located in soma, neurites, axon, and the terminal arborizations. A double-labeling experiment on sections of the locust metathoracic ganglion showed that antisera against glutamate and GABA discriminate between the presumably glutamatergic and GABAergic motor neurons and that GABA-LI-positive neurons are low in Glu-LI. The results suggest that Glu-LI can be used as a marker for detecting potential glutamatergic neurons in insects under the present conditions. Application of the glutamate antiserum to sections of the honeybee brain revealed Glu-LI in motor neurons but also in certain interneurons. The most prominent populations of Glu-LI-positive cells were the monopolar cells and large ocellar interneurons, which are first-order interneurons of the visual and ocellar system. Several groups of descending interneurons also showed Glu-LI. The distributions of Glu-LI and GABA-LI are complementary in locust and bee ganglia. The high level of Glu-LI in certain interneuronal populations, as well as in identified glutamatergic motor neurons, suggests that insect central nervous systems may contain glutamatergic neuronal pathways.
谷氨酸被认为是昆虫骨骼肌兴奋性突触中最有可能的神经递质候选物。我们在石蜡连续切片中研究了蝗虫戊二醛固定的后胸神经节中已鉴定运动神经元的谷氨酸样免疫反应性（Glu-LI）分布。推测为谷氨酸能的快伸胫 motor 神经元和慢伸胫 motor 神经元显示出 Glu-LI，而其他细胞，包括 GABA 能的共同抑制运动神经元和章鱼胺能的背中无对侧细胞簇，染色水平相当低。快伸胫 motor 神经元的免疫反应性位于胞体、神经突、轴突和终末分支中。对蝗虫后胸神经节切片进行的双标记实验表明，针对谷氨酸和 GABA 的抗血清能够区分推测为谷氨酸能和 GABA 能的运动神经元，并且 GABA-LI 阳性神经元的 Glu-LI 含量较低。结果表明，在当前条件下，Glu-LI 可作为检测昆虫潜在谷氨酸能神经元的标记物。将谷氨酸抗血清应用于蜜蜂脑切片显示，运动神经元以及某些中间神经元中存在 Glu-LI。Glu-LI 阳性细胞最显著的群体是单极细胞和大型单眼中间神经元，它们是视觉和单眼系统的一级中间神经元。几组下行中间神经元也显示出 Glu-LI。在蝗虫和蜜蜂神经节中，Glu-LI 和 GABA-LI 的分布是互补的。某些中间神经元群体以及已鉴定的谷氨酸能运动神经元中 Glu-LI 的高水平表明，昆虫中枢神经系统可能包含谷氨酸能神经元通路。
