Hunter C, Petralia R S, Vu T, Wenthold R J
Section on Neurotransmitter Receptor Biology, NIDCD, National Institutes of Health, Bethesda, Maryland 20892.
J Neurosci. 1993 May;13(5):1932-46. doi: 10.1523/JNEUROSCI.13-05-01932.1993.
Glutamate and related amino acids mediate fast excitatory neurotransmission in the vertebrate CNS via ligand-gated cationic channels in the neuronal membrane. These channels are composed of different subunits that assemble into a functional receptor/channel complex. Although studies have shown that these subunits are differentially expressed in neurons, few studies have quantitatively addressed the cell-specific expression of glutamate subunits in relation to known glutamatergic pathways. In the vertebrate auditory system, glutamate is the proposed neurotransmitter of the auditory nerve and parallel fiber pathways. In situ hybridization histochemistry was used to localize AMPA-selective glutamate receptor subunit mRNAs in seven cell types of the rat cochlear nucleus. GluR1-GluR4 AMPA-selective subunits were all expressed in cochlear nucleus neurons; however, the subunits expressed in identified cells varied with the cell type. Granule cells, previously not known to receive glutamatergic input, expressed GluR2 and GluR4 subunits. Cartwheel and stellate interneurons in the dorsal cochlear nucleus, which receive parallel fiber input, expressed all four subunits. Neurons receiving synaptic input from the auditory nerve, including globular, round, spherical, and fusiform cells, expressed GluR2, GluR3, and GluR4 subunits. Furthermore, a subpopulation of round cells in the ventral cochlear nucleus, and fusiform cells in the dorsal cochlear nucleus, expressed the GluR3 subunit at greatly reduced levels compared to neighboring cells. The results confirm the auditory nerve and parallel fiber pathways as glutamatergic and identify a third synaptic population, projecting to granule cells, which is likely glutamatergic. The data suggest that the composition of GluR1-GluR4 subunits on neurons in the cochlear nucleus may be related to presynaptic input; moreover, heterogeneous patterns of expression of the GluR3 subunit, in addition, suggest that variability in mRNA levels within one population of morphologically defined cells is present.
谷氨酸及相关氨基酸通过神经元膜上的配体门控阳离子通道介导脊椎动物中枢神经系统中的快速兴奋性神经传递。这些通道由不同的亚基组成，这些亚基组装成功能性受体/通道复合物。尽管研究表明这些亚基在神经元中差异表达，但很少有研究定量探讨谷氨酸亚基与已知谷氨酸能通路相关的细胞特异性表达。在脊椎动物听觉系统中，谷氨酸被认为是听神经和平行纤维通路的神经递质。原位杂交组织化学被用于在大鼠耳蜗核的七种细胞类型中定位AMPA选择性谷氨酸受体亚基的mRNA。GluR1 - GluR4 AMPA选择性亚基均在耳蜗核神经元中表达；然而，在已识别细胞中表达的亚基随细胞类型而异。颗粒细胞以前未知接受谷氨酸能输入，表达GluR2和GluR4亚基。接受平行纤维输入的耳蜗背核中的车轮状和星状中间神经元表达所有四个亚基。接受来自听神经突触输入的神经元，包括球状、圆形、球形和梭形细胞，表达GluR2、GluR3和GluR4亚基。此外，耳蜗腹核中的圆形细胞亚群以及耳蜗背核中的梭形细胞，与相邻细胞相比，GluR3亚基的表达水平大幅降低。结果证实听神经和平行纤维通路为谷氨酸能通路，并确定了第三个突触群体，投射到颗粒细胞，其可能也是谷氨酸能的。数据表明耳蜗核神经元上GluR1 - GluR4亚基的组成可能与突触前输入有关；此外，GluR3亚基的异质表达模式还表明，在一组形态学定义的细胞内存在mRNA水平的变异性。
