The Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
J Comp Neurol. 2012 Sep 1;520(13):2957-73. doi: 10.1002/cne.23087.
The basal ganglia, including the striatum, globus pallidus interna and externa (GPe), subthalamic nucleus (STN), and substantia nigra pars compacta, are conserved throughout vertebrate phylogeny and have been suggested to form a common vertebrate mechanism for action selection. In mammals, this circuitry is further elaborated by the presence of a dual-output nucleus, the substantia nigra pars reticulata (SNr), and the presence of modulatory input from the cholinergic pedunculopontine nucleus (PPN). We sought to determine whether these additional components of the mammalian basal ganglia are also present in one of the phylogenetically oldest vertebrates, the lamprey. We show, by using immunohistochemistry, tract tracing, and whole-cell recordings, that homologs of the SNr and PPN are present in the lamprey. Thus the SNr receives direct projections from inwardly rectifying γ-aminobutyric acid (GABA)-ergic striatal neurons expressing substance P, but it is also influenced by indirect basal ganglia projections from the STN and potentially the GPe. Moreover, GABAergic SNr projection neurons are tonically active and project to the thalamus and brainstem motor areas. The homolog of the PPN contains both cholinergic and GABAergic neurons and is connected with all the nuclei of the basal ganglia, supporting its proposed role as part of an extended basal ganglia. A separate group of cholinergic neurons dorsal to the PPN corresponds to the descending mesencephalic locomotor region. Our results suggest that dual-output nuclei are part of the ancestral basal ganglia and that the PPN appears to have coevolved as part of a mechanism for action selection common to all vertebrates.
基底神经节包括纹状体、苍白球内、外（GPe）、丘脑下核（STN）和黑质致密部，在脊椎动物系统发育中是保守的，被认为形成了一个用于行动选择的共同脊椎动物机制。在哺乳动物中，这个回路进一步由一个双输出核，即黑质网状部（SNr），以及来自胆碱能脑桥被盖核（PPN）的调制输入的存在而复杂化。我们试图确定这些哺乳动物基底神经节的额外组成部分是否也存在于一种最古老的脊椎动物——七鳃鳗中。我们通过免疫组织化学、束追踪和全细胞记录表明，SNr 和 PPN 的同源物存在于七鳃鳗中。因此，SNr 接收表达 P 物质的内向整流 GABA 能纹状体神经元的直接投射，但它也受到来自 STN 和潜在的 GPe 的间接基底神经节投射的影响。此外，GABA 能 SNr 投射神经元持续活跃，并投射到丘脑和脑干运动区。PPN 的同源物包含胆碱能和 GABA 能神经元，并与基底神经节的所有核团相连，支持其作为扩展基底神经节的一部分的作用。PPN 背侧的一组单独的胆碱能神经元与下行中脑运动区相对应。我们的结果表明，双输出核是祖基底神经节的一部分，而 PPN 似乎是作为所有脊椎动物共有的行动选择机制的一部分共同进化而来的。
