Somogyi P, Takagi H, Richards J G, Mohler H
MRC Anatomical Neuropharmacology Unit, Department of Pharmacology, Oxford, United Kingdom.
J Neurosci. 1989 Jun;9(6):2197-209. doi: 10.1523/JNEUROSCI.09-06-02197.1989.
Two monoclonal antibodies, bd-17 and bd-24, specific for the beta- and alpha-subunit of the GABAA/benzodiazepine receptor/chloride channel complex, respectively, were used to determine the subcellular distribution of immunoreactivity in the cerebellum by electron microscopy. The 2 antibodies showed similar antigen distribution on the plasma membrane (except in the rat; bd-24 does not recognize the rat antigen), but intracellular immunoreactivity was more prevalent for the alpha-subunit. The plasma membrane of all neuronal types was immunopositive. The degree of immunoreactivity varied greatly between different types of cell, but it was stereotyped among individual cells of the same type. Granule cells showed the strongest immunoreactivity, not only on their dendrites which receive synapses from GABA-containing Golgi cell terminals, but also on their somata which do not receive synapses. Stellate and basket cells were somewhat weaker in immunoreactivity. Purkinje cells were only weakly positive on their somatic membrane but stronger on their dendritic shafts and spines. Golgi cells showed negligible if any immunoreactivity. Neurons of the deep cerebellar nuclei were strongly immunopositive along their plasma membrane. Immunoreactivity was strong in cisternae of the endoplasmic reticulum and in the Golgi saccules of stellate and basket cells, variable in Purkinje cells, while granule cells were rarely immunoreactive intracellularly. It is suggested that these differences reflect differences in the turnover of the receptor complex in the different cell types. The synaptic clefts established by boutons of the GABAergic stellate, basket, and Golgi cells were immunopositive, as were many synapses in the deep cerebellar nuclei. However, immunoreactivity was also present along the nonjunctional plasma membrane, and it was concluded that this reflected the distribution of the antigen. The synaptic clefts at the presumed glutamate-releasing parallel and mossy fiber terminals were almost always immunonegative. No immunoreactivity was detected on axons, nerve terminals, or glial cells. The results demonstrate that different neuronal types express the GABAA/benzodiazepine receptor/chloride channel complex to different degrees. The distribution of the receptor complex suggests that the cellular topography of GABAergic influence is not governed by the precise spatial arrangement of the receptors but by the precise placement of the GABA-releasing terminals, a characteristic of the cerebellar circuit.
使用两种单克隆抗体，bd - 17和bd - 24，分别对GABAA/苯二氮䓬受体/氯离子通道复合物的β亚基和α亚基具有特异性，通过电子显微镜确定小脑免疫反应性的亚细胞分布。这两种抗体在质膜上显示出相似的抗原分布（大鼠除外；bd - 24不识别大鼠抗原），但α亚基的细胞内免疫反应性更为普遍。所有神经元类型的质膜均呈免疫阳性。不同类型细胞之间的免疫反应程度差异很大，但在同一类型的单个细胞中是固定不变的。颗粒细胞显示出最强的免疫反应性，不仅在接受含GABA的高尔基细胞终末突触的树突上，而且在不接受突触的胞体上。星状细胞和篮状细胞的免疫反应性稍弱。浦肯野细胞仅在其胞体膜上呈弱阳性，但在其树突干和树突棘上较强。高尔基细胞即使有免疫反应性也可忽略不计。小脑深部核团的神经元沿其质膜呈强免疫阳性。内质网池以及星状细胞和篮状细胞的高尔基囊泡中的免疫反应性很强，浦肯野细胞中的免疫反应性不一，而颗粒细胞在细胞内很少有免疫反应性。提示这些差异反映了不同细胞类型中受体复合物更新的差异。由GABA能星状细胞、篮状细胞和高尔基细胞的终扣形成的突触间隙呈免疫阳性，小脑深部核团中的许多突触也是如此。然而，非连接质膜上也存在免疫反应性，得出的结论是这反映了抗原的分布。推测的释放谷氨酸的平行纤维和苔藓纤维终末处的突触间隙几乎总是免疫阴性。在轴突、神经终末或神经胶质细胞上未检测到免疫反应性。结果表明，不同神经元类型对GABAA/苯二氮䓬受体/氯离子通道复合物的表达程度不同。受体复合物的分布表明，GABA能影响的细胞拓扑结构不是由受体的精确空间排列决定的，而是由释放GABA的终末的精确位置决定的，这是小脑回路的一个特征。
