Zahm D S
Department of Anatomy and Neurobiology, St Louis University School of Medicine, MO 63104.
Neuroscience. 1989;30(1):33-50. doi: 10.1016/0306-4522(89)90351-5.
This paper describes the results of experiments designed to address whether neuron populations giving rise to different ventral pallidal efferent projections are segregated in a manner concordant with the recently described immunohistochemical compartmentation of ventral pallidum. The retrograde transport of horseradish peroxidase conjugated to wheatgerm agglutinin following injections in the ventral tegmental area of Tsai, medial substantia nigra and subthalamic nucleus was charted in relationship to the patterns of immunohistochemical staining in the forebrain following incubation of sections in antisera against substance P, neurotensin or leucine-enkephalin. In some cases the retrograde labeling and immunohistochemical protocols were combined in the same experiment. As a supplement, the electron microscope was utilized to investigate the ultrastructure and synaptic input of projecting cells making up populations of ventral pallidum neurons that project to different efferent targets. The results indicated that the immunocytochemical compartmentation of ventral pallidum observed in our earlier study is reflected in the organization of neurons from which ventral pallidal efferents originate. Thus, axons destined to terminate in the medial parts of substantia nigra and subthalamic nucleus project from neurons located in the lateral, neurotensin immunoreactivity-deficient part of ventral pallidum and the globus pallidus. Fibers en route to the ventral tegmental area originate in neurotensin immunoreactivity-rich medial parts of the ventral pallidum as part of a large cluster of retrogradely labeled neurons that invades several forebrain structures, including the bed nucleus of the stria terminalis, preoptic regions, and the nuclei of the diagonal band. The electron microscopic results provided additional evidence distinguishing the medial and lateral compartments of ventral pallidum. Whereas projection neurons located in both compartments display similar cytologic features, the density of synaptic input to retrogradely labeled perikarya and proximal dendrites following injections in the subthalamic nucleus is significantly greater than that seen following injections in the ventral tegmental area. Although no attempt was made to examine more distal parts of labeled dendrites in the present study, the observation that most dendritic profiles in the medial part of ventral pallidum were less contacted by boutons than their counterparts in the lateral district suggests that the level of innervation of projection neurons is generally lesser in medial ventral pallidum. This hypothesis is further supported by the presence in the medial ventral pallidum of significant numbers of "glial blockades," a cytologic configuration that is clearly capable of preventing functional interactions and is rarely observed in the lateral ventral pallidum...
本文描述了旨在探讨产生不同腹侧苍白球传出投射的神经元群体是否以与最近描述的腹侧苍白球免疫组织化学分区相一致的方式进行分隔的实验结果。在蔡氏腹侧被盖区、黑质内侧和丘脑底核注射结合了麦胚凝集素的辣根过氧化物酶后，对其逆行运输进行了绘图，以研究切片在抗P物质、神经降压素或亮氨酸脑啡肽抗血清中孵育后前脑的免疫组织化学染色模式。在某些情况下，逆行标记和免疫组织化学方案在同一实验中结合使用。作为补充，利用电子显微镜研究了投射到不同传出靶点的腹侧苍白球神经元群体中组成投射细胞的超微结构和突触输入。结果表明，我们早期研究中观察到的腹侧苍白球免疫细胞化学分区反映在腹侧苍白球传出纤维起源的神经元组织中。因此，注定要终止于黑质内侧和丘脑底核内侧部分的轴突，从位于腹侧苍白球外侧、缺乏神经降压素免疫反应性的部分以及苍白球的神经元投射而来。通向腹侧被盖区的纤维起源于腹侧苍白球富含神经降压素免疫反应性的内侧部分，是一大群逆行标记神经元的一部分，这群神经元侵入了几个前脑结构，包括终纹床核、视前区和斜角带核。电子显微镜结果提供了区分腹侧苍白球内侧和外侧分区的额外证据。虽然位于两个分区的投射神经元显示出相似的细胞学特征，但在丘脑底核注射后，逆行标记的胞体和近端树突的突触输入密度明显大于在腹侧被盖区注射后的密度。尽管在本研究中没有尝试检查标记树突的更远端部分，但观察到腹侧苍白球内侧部分的大多数树突轮廓比外侧区域的对应物受到的终扣接触更少，这表明腹侧苍白球内侧投射神经元的神经支配水平通常较低。腹侧苍白球内侧大量存在“胶质屏障”进一步支持了这一假设，“胶质屏障”是一种细胞学构型，显然能够阻止功能相互作用，在腹侧苍白球外侧很少观察到……
