Chen Q, Veenman L, Knopp K, Yan Z, Medina L, Song W J, Surmeier D J, Reiner A
Department of Anatomy and Neurobiology, University of Tennessee-Memphis 38163, USA.
Neuroscience. 1998 Apr;83(3):749-61. doi: 10.1016/s0306-4522(97)00452-1.
Although immunohistochemical studies have typically found the perikarya of striatal projection neurons to be devoid of immunohistochemical labelling for the GluR1 AMPA type glutamate receptor subunit, the striatal neuropil is rich in GluR1 immunolabelling and in situ hybridization histochemistry has indicated the presence of GluR1 message in many striatal neurons. To explore the possibility that GluR1 subunits may be synthesized by many striatal projection neurons, but selectively localized to their dendrites, we have used light-microscopic and electron-microscopic immunohistochemistry in combination with single-cell reverse transcription-polymerase chain reaction. Light-microscopic immunohistochemical studies confirmed the presence of abundant GluR1 immunoreactivity in the striatal neuropil in rats. Perikaryal labelling was restricted to neurons previously identified as parvalbuminergic neurons. Single-cell reverse transcription-polymerase chain reaction for individual striatal neurons in rats confirmed that most striatal projection neurons (i.e. containing either or both substance P message or enkephalin message) make GluR1 message. For example, 94% of enkephalin-containing neurons, 75% of substance P-containing neurons, and 87% of enkephalin and substance P co-containing neurons expressed GluR1 messenger RNA. Electron-microscopic immunohistochemistry revealed that GluR1 immunolabelling was prominent in 61% of dendritic spines and 53% of dendritic shafts. While prominent perikaryal GluR1 immunolabelling was observed only in a small population of interneurons, sparse perikaryal GluR1 immunolabelling was found associated with the rough endoplasmic reticulum, the Golgi apparatus, the outer membranes of the mitochondria, and the outer envelope of the nucleus of about 30% of striatal projection neurons (identified by their non-indented nuclei). These results indicate that striatal projection neurons selectively target GluR1 subunits to their spines and dendritic shafts. Our finding has implications for the functioning of striatal projection neurons and for the general issue of whether neurons can control the subcellular localization of glutamate receptors.
尽管免疫组化研究通常发现纹状体投射神经元的胞体缺乏对AMPA型谷氨酸受体亚基GluR1的免疫组化标记，但纹状体神经毡富含GluR1免疫标记，且原位杂交组织化学显示许多纹状体神经元中存在GluR1信息。为了探究GluR1亚基可能由许多纹状体投射神经元合成，但选择性地定位于其树突的可能性，我们将光学显微镜和电子显微镜免疫组化与单细胞逆转录-聚合酶链反应相结合。光学显微镜免疫组化研究证实大鼠纹状体神经毡中存在丰富的GluR1免疫反应性。胞体标记仅限于先前鉴定为小白蛋白能神经元的神经元。对大鼠单个纹状体神经元进行单细胞逆转录-聚合酶链反应证实，大多数纹状体投射神经元（即含有P物质信息或脑啡肽信息之一或两者）产生GluR1信息。例如，94%的含脑啡肽神经元、75%的含P物质神经元以及87%的同时含脑啡肽和P物质的神经元表达GluR1信使核糖核酸。电子显微镜免疫组化显示，61%的树突棘和53%的树突干中有明显的GluR1免疫标记。虽然仅在一小部分中间神经元中观察到明显的胞体GluR1免疫标记，但在约30%的纹状体投射神经元（通过其无凹陷的细胞核鉴定）中，发现稀疏的胞体GluR1免疫标记与粗面内质网、高尔基体、线粒体外膜和细胞核外膜有关。这些结果表明，纹状体投射神经元将GluR1亚基选择性地靶向其树突棘和树突干。我们的发现对纹状体投射神经元的功能以及神经元是否能够控制谷氨酸受体的亚细胞定位这一普遍问题具有启示意义。
