Pickel V M, Towle A C, Joh T H, Chan J
Division of Neurobiology, Cornell University Medical College, New York, New York 10021.
J Comp Neurol. 1988 Jun 1;272(1):1-14. doi: 10.1002/cne.902720102.
Neurons containing gamma-aminobutyric acid (GABA) in the medial portion of the adult rat nucleus accumbens were characterized with respect to their ultrastructure, sites of termination, and catecholaminergic input. Antisera against GABA-conjugates and the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH), were localized within single sections by means of peroxidase-antiperoxidase (PAP) and immunoautoradiographic labeling methods. Peroxidase reaction product indicating GABA-like immunoreactivity (GABA-LI) was seen in medium-size (15-20 microns) perikarya containing either round and unindented or invaginated nuclear membranes. The cells with invaginated nuclei were few in number and usually exhibited more intense peroxidase reaction product in sections collected at the same distance from the surface of the tissue. Reaction product for GABA was also detected in proximal (1.5-3.0 microns) dendrites, axons, and terminals. Terminals with GABA-LI formed symmetric junctions on perikarya, proximal dendrites, and dendritic spines of neurons that usually lacked detectable immunoreactivity. Many of the GABAergic terminals also were apposed directly to other unlabeled terminals and to terminals exhibiting either peroxidase labeling for GABA or immunoautoradiographic labeling for TH. Many of the unlabeled terminals associated with the GABAergic axons formed asymmetric junctions on dendritic spines. From 138 TH-labeled, principally dopaminergic terminals that were examined in the medial nucleus accumbens, 4% were associated with the somata of GABAergic neurons and another 14% formed symmetric junctions with proximal dendrite showing GABA-LI. The remaining TH-immuno-reactive terminals either lacked recognizable densities or formed symmetric synapses on unlabeled dendrites and spines. A few of the unlabeled dendrites, as well as those containing GABA-LI, received symmetric synapses from both catecholaminergic and GABAergic terminals. We conclude that in the medial portion of the rat nucleus accumbens, GABA is localized to two morphologically distinct types of neurons, one or both of which receive monosynaptic input from catecholaminergic afferents, and that GABAergic terminals form symmetric synapses on other principally non-GABAergic neurons. The results also support earlier physiological evidence showing that GABA may modulate the output of other GABAergic and non-GABAergic neurons through presynaptic associations.
对成年大鼠伏隔核内侧部分中含有γ-氨基丁酸（GABA）的神经元，从其超微结构、终末部位及儿茶酚胺能输入方面进行了特征描述。采用过氧化物酶-抗过氧化物酶（PAP）和免疫放射自显影标记法，将抗GABA结合物和儿茶酚胺合成酶酪氨酸羟化酶（TH）的抗血清定位在单个切片内。显示GABA样免疫反应性（GABA-LI）的过氧化物酶反应产物见于中等大小（15 - 20微米）的胞体，其核膜呈圆形且无凹陷或有内陷。核内陷的细胞数量较少，并且在距组织表面相同距离处收集的切片中通常显示出更强的过氧化物酶反应产物。在近端（1.5 - 3.0微米）树突、轴突和终末中也检测到了GABA的反应产物。具有GABA-LI的终末在通常缺乏可检测免疫反应性的神经元的胞体、近端树突和树突棘上形成对称突触。许多GABA能终末还直接与其他未标记的终末以及显示GABA过氧化物酶标记或TH免疫放射自显影标记的终末相邻。许多与GABA能轴突相关的未标记终末在树突棘上形成不对称突触。在伏隔核内侧部分检查的138个TH标记的、主要为多巴胺能的终末中，4%与GABA能神经元的胞体相关，另外14%与显示GABA-LI的近端树突形成对称突触。其余TH免疫反应性终末要么缺乏可识别的致密物，要么在未标记的树突和树突棘上形成对称突触。少数未标记的树突以及含有GABA-LI的树突，接受来自儿茶酚胺能和GABA能终末的对称突触。我们得出结论，在大鼠伏隔核内侧部分，GABA定位于两种形态学上不同类型的神经元，其中一种或两种接受来自儿茶酚胺能传入纤维的单突触输入，并且GABA能终末在其他主要为非GABA能的神经元上形成对称突触。这些结果也支持了早期的生理学证据，表明GABA可能通过突触前联系调节其他GABA能和非GABA能神经元的输出。
