Caserta M T, Barker J L
Laboratory of Neurophysiology, National Institute of Neurological Diseases and Stroke, Bethesda, MD 20892, USA.
Int J Dev Neurosci. 1994 Dec;12(8):753-65. doi: 10.1016/0736-5748(94)90055-8.
Murine spinal cord and dorsal root ganglion GABAergic neurons, derived from 12-day-old fetuses, were examined autoradiographically, biochemically and immunocytochemically in vitro to determine the timecourse of appearance and maturation of this phenotype and the extent and mode of its innervation of target neurons. Specific 3H-GABA uptake into spinal cord neurons was the first property to develop and was present at the earliest time studied, one day in vitro. Immunocytochemical localization of glutamic acid decarboxylase (GAD) revealed positively stained neurons beginning at four days. At five days in vitro, electron microscopic immunocytochemistry revealed GAD-immunoreactive (GAD-IMR) boutons investing neuronal perikarya as well as neuronal processes. By one week in vitro, GAD-IMR neurons constituted 27% of the total population and GAD-IMR boutons could be seen contacting every cell with a neuronal morphology. The mode of investment of target neurons by GAD-IMR boutons was not circumscribed to either soma or dendrites but usually involved the entire neuronal perimeter and did not change with time in culture. Three morphologically distinct types of GAD-IMR neurons were evident: a small, bipolar type; a medium-sized multipolar neuron which was the most common and a large, multipolar type, resembling a motoneuron. A small population (8%) of dorsal root ganglion neurons was found to contain GAD both biochemically and immunocytochemically but was never invested by GAD-IMR boutons. GAD activity in vitro paralleled in vivo levels with maximal activity being reached at four weeks in vitro and 10 days postnatally in the intact mouse spinal cord. Murine spinal cord GABAergic neurons are a morphologically diverse and abundant neuronal population with extensive, precocious innervation of all other neuronal phenotypes in vitro suggesting that GABA has a widespread influence over other developing neuronal systems in the murine spinal cord.
对源自12日龄胎儿的小鼠脊髓和背根神经节GABA能神经元进行了体外放射自显影、生化和免疫细胞化学检查，以确定该表型出现和成熟的时间进程，以及其对靶神经元的支配范围和方式。脊髓神经元对特异性3H-GABA的摄取是最早出现的特性，在体外培养的第一天，即研究的最早时间就已存在。谷氨酸脱羧酶（GAD）的免疫细胞化学定位显示，从体外培养四天开始就有呈阳性染色的神经元。体外培养五天时，电子显微镜免疫细胞化学显示，GAD免疫反应性（GAD-IMR）终末围绕神经元胞体以及神经突起。到体外培养一周时，GAD-IMR神经元占神经元总数的27%，可见GAD-IMR终末与每一个具有神经元形态的细胞相接触。GAD-IMR终末对靶神经元的支配方式并不局限于胞体或树突，而是通常涉及整个神经元周边，并且在培养过程中不会随时间变化。明显有三种形态不同的GAD-IMR神经元类型：一种小的双极型；一种中等大小的多极神经元，这是最常见的类型；还有一种大的多极型，类似于运动神经元。发现一小部分（8%）背根神经节神经元在生化和免疫细胞化学方面都含有GAD，但从未被GAD-IMR终末支配。体外GAD活性与体内水平平行，在体外培养四周和完整小鼠脊髓出生后10天时达到最大活性。小鼠脊髓GABA能神经元是一个形态多样且数量丰富的神经元群体，在体外对所有其他神经元表型具有广泛、早熟的支配作用，这表明GABA对小鼠脊髓中其他发育中的神经元系统具有广泛影响。
