Karle E J, Anderson K D, Medina L, Reiner A
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163, USA.
J Comp Neurol. 1996 May 20;369(1):109-24. doi: 10.1002/(SICI)1096-9861(19960520)369:1<109::AID-CNE8>3.0.CO;2-7.
A dopaminergic projection from the midbrain to the striatal portion of the basal ganglia is present in reptiles, birds, and mammals. Although the ultrastructure of these fibers and terminals within the striatum has been studied extensively in mammals, little information is available on the ultrastructure of this projection in nonmammals. In the present study, we used immunohistochemical labeling with antibodies against tyrosine hydroxylase (TH) or dopamine (DA) to study the dopaminergic input to the striatal portion of the basal ganglia in pigeons (i.e., lobus parolfactorius and paleostriatum augmentatum). At the light microscopic level, the anti-TH and anti-DA revealed a similar abundance and distribution of numerous labeled fine fibers and varicosities within the striatum. In contrast, the use of an antidopamine beta-hydroxylase antiserum (which labels only adrenergic and noradrenergic terminals) labeled very few striatal fibers, which were restricted to visceral striatum. These results demonstrate that anti-TH mainly labels dopaminergic terminals in the striatum. At the electron microscopic level, the anti-TH and anti-DA antisera labeled numerous axon terminals within the striatum (15-20% of all striatal terminals). These terminals tended to be small (with an average length of 0.6 microns) and flattened, and their vesicles tended to be small (35-60 nm in diameter) and pleomorphic. About 50% of the terminals were observed to make synaptic contacts in the planes of section examined, and nearly all of these synaptic contacts were symmetric. Both TH+ and DA+ terminals typically contacted dendritic shafts or the necks of dendritic spines, but a few contacted perikarya. No clear differences were observed between TH+ and DA+ terminals within medial striatum (whose neurons project to the nigra in birds) or between TH+ and DA+ terminals within lateral striatum (whose neurons project to the pallidum in birds). In addition, no differences were observed between medial and lateral striata in either TH+ or DA+ terminals. Thus, there is no evident difference in pigeons between striatonigral and striatopallidal neurons in their dopaminergic innervation. Our results also indicate that the abundance, ultrastructural characteristics, and postsynaptic targets of the midbrain dopaminergic input to the pigeon striatum are highly similar to those in mammals. This anatomical similarity is consistent with the pharmacologically demonstrable similarity in the role of the dopaminergic input to the striatum in birds and mammals.
从中脑到基底神经节纹状体部分的多巴胺能投射存在于爬行动物、鸟类和哺乳动物中。尽管在哺乳动物中已对纹状体内这些纤维和终末的超微结构进行了广泛研究，但关于非哺乳动物中该投射的超微结构的信息却很少。在本研究中，我们使用针对酪氨酸羟化酶（TH）或多巴胺（DA）的抗体进行免疫组织化学标记，以研究鸽子基底神经节纹状体部分（即副嗅叶和新纹状体增大部）的多巴胺能输入。在光学显微镜水平，抗TH和抗DA显示纹状体内大量标记的细纤维和膨体具有相似的丰度和分布。相比之下，使用抗多巴胺β-羟化酶抗血清（仅标记肾上腺素能和去甲肾上腺素能终末）标记的纹状体纤维很少，仅限于内脏纹状体。这些结果表明抗TH主要标记纹状体内的多巴胺能终末。在电子显微镜水平，抗TH和抗DA抗血清标记了纹状体内大量轴突终末（占所有纹状体终末的15 - 20%）。这些终末往往较小（平均长度为0.6微米）且扁平，其囊泡往往较小（直径35 - 60纳米）且形态多样。在所检查的切片平面中观察到约50%的终末形成突触联系，并且几乎所有这些突触联系都是对称的。TH +和DA +终末通常与树突干或树突棘的颈部接触，但有少数与胞体接触。在纹状体内侧（其神经元投射到鸟类的黑质）的TH +和DA +终末之间或纹状体外侧（其神经元投射到鸟类的苍白球）的TH +和DA +终末之间未观察到明显差异。此外，在TH +或DA +终末方面，内侧和外侧纹状体之间也未观察到差异。因此，在鸽子中，黑质纹状体和苍白球纹状体神经元的多巴胺能神经支配没有明显差异。我们的结果还表明，中脑多巴胺能输入到鸽子纹状体的丰度、超微结构特征和突触后靶点与哺乳动物中的高度相似。这种解剖学上的相似性与鸟类和哺乳动物中多巴胺能输入到纹状体的作用在药理学上可证明的相似性是一致的。
