Huang Jie, Pickel Virginia M
Division of Neurobiology, Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA.
J Neurocytol. 2002 Sep-Nov;31(8-9):667-79. doi: 10.1023/a:1025795729393.
Serotonergic transmission is terminated by serotonin transporter (SERT)-mediated uptake following activation of serotonin receptors, several subtypes of which are present in the medial nucleus of the solitary tract (mNTS) at the area postrema level. In this region, serotonin (5HT) is a major modulator of the baroreceptor reflex and also affects gastric motility. This serotonin is derived from multiple sources including local neurons and inputs from raphe and visceral vagal afferents. To determine the relevant functional sites for serotonin uptake in the mNTS, we examined the electron microscopic localization of SERTs using both immunoperoxidase and immunogold labeling in rat brain. In addition, we combined these methods for dual labeling of SERTs and 5HT2A receptors to detect whether the SERT in this region was located near or at a distance from the sites of activation of these G-protein coupled receptors. Intensive SERT immunolabeling was seen on plasma membranes of axons and morphologically heterogeneous axon terminals that formed symmetric or asymmetric synapses on dendrites without detectable 5HT2A immunoreactivity (IR). 5HT2A-IR was, however, located in other nearby neuronal and glial profiles, some of which apposed intensively SERT-labeled terminals or terminals containing lower intensity of SERT immunolabeling. In somatodendritic profiles, co-expression of SERT and 5HT2A receptor immunolabeling was seen near synapses and Golgi lamellae. Our results suggest that in the mNTS 5HT activates 5HT2A receptors at a distance from SERT-mediated uptake sites in diverse cell types including some that express both 5HT2A receptors and SERTs.
5-羟色胺能传递在5-羟色胺受体激活后，通过5-羟色胺转运体（SERT）介导的摄取而终止，其中几种亚型存在于最后区水平的孤束核内侧核（mNTS）中。在该区域，5-羟色胺（5HT）是压力感受器反射的主要调节因子，也影响胃动力。这种5-羟色胺来源于多种来源，包括局部神经元以及中缝和内脏迷走传入神经的输入。为了确定mNTS中5-羟色胺摄取的相关功能位点，我们在大鼠脑中使用免疫过氧化物酶和免疫金标记检查了SERT的电子显微镜定位。此外，我们将这些方法结合用于SERT和5HT2A受体的双重标记，以检测该区域中的SERT是否位于这些G蛋白偶联受体激活位点的附近或远处。在轴突的质膜和形态异质的轴突终末上观察到强烈的SERT免疫标记，这些轴突终末在树突上形成对称或不对称突触，而没有可检测到的5HT2A免疫反应性（IR）。然而，5HT2A-IR位于附近的其他神经元和神经胶质细胞中，其中一些与强烈SERT标记的终末或SERT免疫标记强度较低的终末相邻。在体树突状结构中，在突触和高尔基体薄片附近可见SERT和5HT2A受体免疫标记的共表达。我们的结果表明，在mNTS中，5HT在距离SERT介导的摄取位点一定距离处激活5HT2A受体，这些摄取位点存在于多种细胞类型中，包括一些同时表达5HT2A受体和SERT的细胞。
