Sakai S T, Patton K
Department of Anatomy, College of Human Medicine, Michigan State University, East Lansing 48824.
J Comp Neurol. 1993 Apr 8;330(2):183-94. doi: 10.1002/cne.903300204.
The distribution of nigrothalamic and cerebellothalamic projections was investigated in the dog by a double labeling strategy combining the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and tritiated amino acids. Following tritiated amino acid injections into the substantia nigra pars reticulata (SNr) and WGA-HRP injections into the contralateral cerebellar nuclei, we found that the nigrothalamic and cerebellothalamic afferents distribute to three main targets: the central portion of the ventral anterior nucleus (VA) and the ventral lateral nucleus (VL), the internal medullary lamina (IML) region, which includes the paralaminar VA, the mediodorsal nucleus (MD) and the central lateral nucleus (CL), and finally the ventromedial nucleus (VM). We observed three distribution patterns of labeled fibers: a) Dense single label was observed in the central portion of VA following the SNr injections and in VL following the cerebellar nuclei injections. b) A complementary pattern consisting of alternating foci of nigral and cerebellar label was found in the IML region. This pattern was also observed in the caudal intralaminar nuclei where cerebellar label predominated in the centrum medianum (CM), while the parafascicular nucleus (Pf) primarily contained nigral label. c) An overlapping pattern of autoradiographic and WGA-HRP label was found in the lateral half of the VM. Overall, the distribution of nigrothalamic and cerebellothalamic projections was widespread throughout much of rostrocaudal thalamus. However, the pattern of projections varied along a continuum from lateral to medial thalamus. In lateral thalamus, nigral and cerebellar projections distributed to separate nuclei while in medial thalamus, the projection pattern changed to focal and complementary in the IML and overlapping in VM. Taken together, these thalamic projections may constitute crucial links in different functional channels involved in alerting and orienting mechanisms associated with motor behavior. Our findings also suggest that the organization of motor thalamic afferents in the dog shares similarities with the segregated and parallel circuitry characteristic of primates as well as with the overlapping and converging circuits of rodents and other carnivores.
采用结合了与辣根过氧化物酶结合的小麦胚芽凝集素（WGA-HRP）的顺行运输和氚化氨基酸的双重标记策略，在犬类中研究了黑质丘脑和小脑丘脑投射的分布。在将氚化氨基酸注射到黑质网状部（SNr）并将WGA-HRP注射到对侧小脑核之后，我们发现黑质丘脑和小脑丘脑传入纤维分布到三个主要靶点：腹前核（VA）和腹外侧核（VL）的中央部分、包括旁层VA、背内侧核（MD）和中央外侧核（CL）的内髓板（IML）区域，以及最后腹内侧核（VM）。我们观察到标记纤维的三种分布模式：a）在注射SNr后，VA中央部分观察到密集的单一标记，在注射小脑核后，VL观察到密集的单一标记。b）在IML区域发现了由黑质和小脑标记交替焦点组成的互补模式。在尾侧板内核中也观察到这种模式，其中小脑标记在中央中核（CM）中占主导，而束旁核（Pf）主要包含黑质标记。c）在VM的外侧半部发现了放射自显影和WGA-HRP标记的重叠模式。总体而言，黑质丘脑和小脑丘脑投射的分布在丘脑的大部分前后区域广泛存在。然而，投射模式从丘脑外侧到内侧沿连续体变化。在丘脑外侧，黑质和小脑投射分布到不同的核，而在丘脑内侧，投射模式在IML中变为焦点性和互补性，在VM中变为重叠性。综上所述，这些丘脑投射可能构成与运动行为相关的警觉和定向机制所涉及的不同功能通道中的关键环节。我们的研究结果还表明，犬类运动丘脑传入纤维的组织与灵长类动物的分离和平行电路特征以及啮齿动物和其他食肉动物的重叠和汇聚电路具有相似性。
