The first developing "mixed" synapses between vestibular sensory neurons mediate glutamate chemical transmission.
The first developing "mixed" synapses between vestibular sensory neurons mediate glutamate chemical transmission.
复制标题
前庭感觉神经元之间第一个发育的“混合”突触介导谷氨酸化学传递。
DOI：
10.1016/0306-4522(94)90158-9
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发表时间：
1994
期刊：
影响因子：
3.3
通讯作者：
Giaume,C
中科院分区：
文献类型：
--
作者：
Peusner,KD;Giaume,C
在本研究中，确定了由前庭神经刺激鸡切向核主细胞产生单相电位的突触传递的性质。这项工作是在关键胚胎期15-16天的切片准备中进行的，这是第一次观察到轴体末端被称为勺状末端的形态混合(化学和电)突触的时间。勺端由直径最大的初级前庭纤维--巨大的前庭纤维组成。这种单相电位符合化学而不是电传递的标准，因为在大多数情况下，由于以下反应：(I)主细胞去极化引发的直接棘波与前庭诱发的动作电位之间没有碰撞；(Ii)未能遵循高频刺激(高达50赫兹)；(Iii)对低钙溶液(0.1 mM)的敏感性。这些试验表明，在这个阶段，勺端和主细胞之间的强烈电耦合并不占优势。这些记录是从细胞内注射了生物细胞素的主细胞中获得的，从而可以通过形态标准来鉴定它们。染色的主细胞与其支配前庭纤维之间缺乏示踪剂偶联(n=17)，这与电偶联的缺乏是一致的。通过应用谷氨酸受体拮抗剂dl-2-氨基-5-磷酸戊酸(40μM)和6-氰基-7-硝基-2，3-二酮(10μM)可逆地阻断前庭神经传递，鉴定了参与前庭反应的神经递质。这些结果表明，在这些“混合”前庭突触形成之初，从形态上确定的缝隙连接可能没有功能，主细胞对前庭神经刺激的主要反应是由谷氨酸介导的。
In the present study, the nature of the synaptic transmission responsible for a monophasic potential generated by vestibular nerve stimulation of the principal cells in the chick tangential nucleus was established. This work was performed in slice preparations at the critical embryonic age of 15–16 days, the time of first observation of morphologically mixed (chemical and electrical) synapses at the axosomatic endings called spoon endings. The spoon endings are formed by the primary vestibular fibers with the largest diameters, the colossal vestibular fibers. This monophasic potential fits the criteria for chemical rather than electrical transmission due to the following responses in most cases: (i) the absence of collision between a direct spike initiated by depolarization in the principal cell and a vestibular-evoked action potential; (ii) failure to follow high frequency stimulation (up to 50 Hz); (iii) sensitivity to low calcium solution (0.1 mM). These tests indicate that strong electrical coupling between spoon endings and principal cells does not prevail at this stage. The recordings were obtained from principal cells injected intracellularly with biocytin, allowing their identification by morphological criteria. The lack of tracer coupling between the stained principal cells and their innervating vestibular fibers (n= 17) is consistent with the absence of electrical coupling. Identification of the neurotransmitter involved in this vestibular response was achieved by bath application of glutamate receptor antagonists,dl-2-amino-5-phosphonovaleric acid (40 μM) and 6-cyano-7-nitro-quinoxaline-2,3-dione (10 μM), which blocked transmission reversibly.These results suggest that at the onset of formation of these “mixed” vestibular synapses, the gap junctions identified morphologically are likely not functional, and that the main response of the principal cells to vestibular nerve stimulation is mediated by glutamate.