Márin O, Smeets W J, González A
Departamento de Biología Celular, Facultad de Biología, Universidad Complutense, Madrid, Spain.
J Comp Neurol. 1997 Jul 7;383(3):349-69. doi: 10.1002/(sici)1096-9861(19970707)383:3<349::aid-cne6>3.0.co;2-3.
To broaden our insight into the organization of the basal ganglia of amphibians, the development of the connections of the striatum and the nucleus accumbens was studied by means of tract-tracing techniques based on the transport of biotinylated dextran amines. In a number of experiments, these techniques were combined with tyrosine hydroxylase immunohistochemistry to identify the sources of catecholaminergic inputs to the striatum and the nucleus accumbens. Already at late embryonic stages, the basal telencephalon receives inputs from cells located in the amygdala, the thalamus, the suprachiasmatic nucleus, the raphe nucleus, and the rhombencephalic reticular formation. At these stages, the rostral part of the posterior tubercle seems to be the only source of the dopaminergic input to the basal telencephalon. During premetamorphosis, not only a differentiation between connections of the striatum and the nucleus accumbens could be made, but new sources of inputs were also detected in the mesencephalic and isthmic tegmentum, the parabrachial nucleus, and the nucleus of the solitary tract. Double-labeling experiments revealed that, at these stages, in addition to the posterior tubercle, cells within the mesencephalic tegmentum, the locus coeruleus, and the solitary tract nucleus contribute to the catecholaminergic innervation of the basal forebrain. During prometamorphic stages, a gradual increase occurs in the number of cells that project to the basal telencephalon. At the beginning of the metamorphic climax, the organization of the basal ganglia afferents largely resembles the pattern observed in juveniles and adults. Remarkably, during larval stages, the cells that contribute to the dopaminergic innervation of the basal forebrain show a rostrocaudal gradient in time of appearance. Moreover, the dopaminergic fibers reach the striatum earlier than the nucleus accumbens, and they precede markedly the development of the efferent connections of both brain structures. These developmental aspects are easily correlated with the situation in amniotes; therefore, the notion that amphibians share an essentially similar pattern of basal ganglia organization with other tetrapods is further strengthened.
为了更深入地了解两栖动物基底神经节的组织结构，我们采用基于生物素化葡聚糖胺转运的示踪技术，研究了纹状体和伏隔核连接的发育过程。在一些实验中，这些技术与酪氨酸羟化酶免疫组织化学相结合，以确定纹状体和伏隔核的儿茶酚胺能输入来源。早在胚胎后期，端脑基部就接受来自杏仁核、丘脑、视交叉上核、中缝核和后脑网状结构中细胞的输入。在这些阶段，后结节的前部似乎是端脑基部多巴胺能输入的唯一来源。在变态前阶段，不仅可以区分纹状体和伏隔核的连接，还在中脑和峡部被盖、臂旁核和孤束核中检测到新的输入来源。双重标记实验表明，在这些阶段，除了后结节外，中脑被盖、蓝斑和孤束核内的细胞也对基底前脑的儿茶酚胺能神经支配有贡献。在变态前阶段，投射到端脑基部的细胞数量逐渐增加。在变态高潮开始时，基底神经节传入纤维的组织结构与幼体和成体中观察到的模式基本相似。值得注意的是，在幼体阶段，对基底前脑多巴胺能神经支配有贡献的细胞在出现时间上呈现出从前向后的梯度。此外，多巴胺能纤维比伏隔核更早到达纹状体，并且明显先于这两个脑结构传出连接的发育。这些发育方面的情况很容易与羊膜动物的情况相关联；因此，两栖动物与其他四足动物共享基本相似的基底神经节组织模式这一观点得到了进一步加强。
