大鼠运动皮层投射神经元与Parvalbumin免疫阳性神经纤维终末的关系──免疫荧光、Confocal显微镜观察

THE DISTRIBUTION PATTERNS OF PARVALBUMIN IMMUNOREACTIVE APPOSITIONS ON PROJECTION NEURONS OF RAT MOTOR CORTEX BY MEANS OF LUCIFER YELLOW INTRACELLULAR STAINING, IMMUNOFLUORESCENCE AND CONFOCAL MICROSCOPE

Parvalburnin是细胞内一种钙结合蛋白。同时又可作为中枢神经系统内与GABA共存的神经元亚群的特异标记物，主要标记篮状及苔烛细胞。用PAP方谈染色可见大鼠Parvalbumin免疫阳性神经终末在运动皮层锥体神经元胞体周围形成包篮现象，但因该方法的局限性．较难明确二者的关系。为进一步了解Parvalbumin阳性终未在锥体神经元脑体、树突与轴突整体上的分布状况以及运幼皮层内不同传出神经元是否均接受同样的支配，本实验利用FastBlue送行标记、固定脑片细胞内注入LueiferYellow结合免疫荧光、Confocal显微镜观察，研究运动皮层内皮质丘脑（束旁核）、皮质效状体及皮质脊髓三种投射神经元与Parvalbumin阳性终末的关系。通过1．μ连续扫描图像的分析及立体对观察，Parvalbumin阳性终末清晰可见，与LuciferYellow标记的锥体细胞的关系也容易辨别．在三种投射神经元胞体上均可见Parvalbumin阳性终末包绕，形成明显包篮现象，但三种神经元上的终末数未见明显区别·阳性终未还分布于近端树突上，距胞体越远越稀疏：但在距脑体50μm以上的顶树突、30μm以上的基树突及其二、三级分枝的远端树突上仍偶有终末分布．此外，三种神经元轴突起始段上也有少量终末接触，但未形成明显的cartridge现象．这一结果揭示。

Parvalbumin (PV), as a kind of caIcium binding protein, is a specific marker of cortical GABAergic neuronal sub-types. In the previous study of PV immunoreactivity, we noted that the PV-ir terrninals mostly surrounded the somata of pyramidal neurons to form pericelluar baskets. To futher determine the relationships between the PV-ir terminals and the different proection neurons of motor cortex, especially their spatial distribution patterns on dendrites and axons of these neurons, a combination of Lucifer yellow (LY) intracellular injection of fast blue retrogradely-labeled neurons and PV-im-munofluorescence,confocal microscopic observation were utilized in this study. The PV-ir cell bodies, dendrites and termi-nals and the LY-labeled corticothalamic (CTN), corticostriatal (CSN) and pyramidal tract neuron (PTN) were simultane-ously characterized through the serial optical section, cornputer-aided reconstruction and stereo-pair analysis. The terminal boutons around the somata of all three kinds of neurons formed pericellular baskets, but there were no significant differences among them. However, the close apposition and spatial relationship between them were much easier identified. In addition,the number of labeled terminals on the proxirnal and distal dendrites were gradually decreased from sorna. These boutons were also occasionally observed on axon initial segment (AIS), but no cartridge were forrned. This data indicated that the sorna, proximal and distal dendrite as well as AIS of three kinds of projection neurons in rat rnotor cortex received similar in-trinsic GABAergic PV-ir innervation.