5-HYDROXYDOPAMINE-LABELED DOPAMINERGIC AXONS - 3-DIMENSIONAL RECONSTRUCTIONS OF AXONS, SYNAPSES AND POSTSYNAPTIC TARGETS IN RAT NEOSTRIATUM
5-HYDROXYDOPAMINE-LABELED DOPAMINERGIC AXONS - 3-DIMENSIONAL RECONSTRUCTIONS OF AXONS, SYNAPSES AND POSTSYNAPTIC TARGETS IN RAT NEOSTRIATUM
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DOI：
10.1016/0306-4522(94)90084-1
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发表时间：
1994-02-01
期刊：
影响因子：
3.3
通讯作者：
YOUNG, SJ
中科院分区：
文献类型：
--
作者：
GROVES, PM;LINDER, JC;YOUNG, SJ
以前的研究采用5-羟多巴胺，以确定黑质纹状体多巴胺能轴突和它们的突触发现，标记的轴突很少突触或不对称的接触占主导地位。相反，最近的研究使用酪氨酸羟化酶或多巴胺抗体技术表明，假定多巴胺能轴突形成小的对称接触。我们重新检查5-羟基多巴胺标记的材料，从大鼠新纹状体使用系列三维重建技术的标记轴突，突触和突触后靶的形态特征。这种超微结构分析揭示了一类高度标记的轴突是小的（直径0.06-1.5 μ m），缺乏大的静脉曲张。这些轴突形成小的（0.011-0.09 μ m（2））、传递的、对称的突触，主要在树突棘和多刺的树突轴上，在某些情况下，在分支点附近的多刺树突节段上。这些突触沿着轴突的网站出现无关的轴突扩大的位置，这表明计数静脉曲张可能不是一个准确的指示多巴胺能神经支配的程度在新纹状体。这些5-羟基多巴胺标记的元素的特性在所有方面都对应于在以前的研究中通过免疫组织化学鉴定为多巴胺能的轴突和突触。在组织中，所有标记和未标记的突触进行了分类，约9%的所有突触被确定为多巴胺能由这种类型的label.Three-dimensional重建提供了额外的见解有关的相互作用的多巴胺能传入与突触后纹状体的目标和他们的关系，其他传入这些神经元。他们揭示了一个短的、无分支的多巴胺能轴突段可以在树突棘、轴和一个或多个树突的分支点上形成多个突触。此外，一个树突可以接收来自多个标记轴突的接触。棘上的多巴胺突触总是与同一棘上的未标记的、不对称的突触联系在一起，具有明显不同的、较轻的标记形式的各种形态的突触要罕见得多，可能代表了新纹状体的其他胺能传入。早期5-羟基多巴胺研究中第二种形式标记的存在可能导致了对不同技术检查的多巴胺能突触外观的长期争议。我们的研究结果有助于解决这一争议，并证实黑质纹状体投射使小对称突触与各种纹状体的目标。
Previous studies employing 5-hydroxydopamine to identify nigrostriatal dopaminergic axons and their synapses found that labeled axons made few synapses or that asymmetric contacts predominated. In contrast, recent studies using tyrosine hydroxylase or dopamine antibody techniques indicate that presumed dopaminergic axons form small symmetric contacts. We re-examined 5-hydroxydopamine-labeled material from the rat neostriatum using serial three-dimensional reconstruction techniques to characterize the morphology of labeled axons, synapses and postsynaptic targets. This ultrastructural analysis revealed a class of heavily labeled axons that are small (0.06-1.5 mu m in diameter) and lack large varicosities. These axons form small (0.011-0.09 mu m(2)), en passant, symmetric synapses, mainly onto dendritic spines and spiny dendritic shafts and, in some cases, onto aspiny dendritic segments near branch points. The sites of these synapses along the axon appeared unrelated to the locations of axonal enlargements; suggesting that counting varicosities may not be an accurate indication of the extent of dopaminergic innervation in the neostriatum. The characteristics of these 5-hydroxydopamine-labeled elements correspond in all respects to axons and synapses identified as dopaminergic by immunohistochemistry in previous studies. In tissue in which all labeled and unlabeled synapses were classified, approximately 9% of all synapses were identified as dopaminergic by this type of label.Three-dimensional reconstructions provided additional insight concerning the interaction of dopaminergic afferents with postsynaptic striatal targets and their relation to other afferents to these neurons. They reveal that a short, unbranched dopaminergic axonal segment can make multiple synapses onto dendritic spines, shafts and branch points of one or more dendrites. In addition, one dendrite can receive contacts from several labeled axons. Dopamine synapses onto spines are always associated with unlabeled, asymmetric synapses onto the same spine.Synapses of various morphologies with a distinctly different, lighter form of labeling were much rarer, and may represent other aminergic afferents to the neostriatum. The presence of this second form of label in earlier 5-hydroxydopamine studies may have contributed to the long-standing controversy over the appearance of dopaminergic synapses examined by different techniques. Our results help to resolve this controversy and confirm that the nigrostriatal projection makes small symmetric synapses with a variety of striatal targets.