Winer J A, Wenstrup J J, Larue D T
Department of Molecular and Cell Biology, University of California, Berkeley 94720-2097.
J Comp Neurol. 1992 May 1;319(1):172-90. doi: 10.1002/cne.903190114.
The anatomy and the spatial distribution of neurons and axonal endings (puncta) immunoreactive for glutamic acid decarboxylase (GAD) or gamma-aminobutyric acid (GABA) were studied in the medial geniculate body of the mustached bat (Pteronotus parnellii). The principal findings are that: 1) most GABAergic neurons are present in the dorsal and ventral divisions with few, if any, in the medial division; 2) only a small fraction, about 1% or less, of auditory thalamic neurons are immunopositive; 3) the density of immunoreactive puncta is independent on the number of GABAergic neurons in the thalamic divisions, with the ventral division having the largest number/unit area, the medial division about 75% of this value, and the dorsal division only about 50%; and 4) the form of the puncta was unique to each division, those in the ventral division being medium-sized and comparatively simple, those in the medial division predominantly large, coarse, and complex, while dorsal division ending were finer and more delicate. These patterns recapitulate, with some significant exceptions, those found in the rat and cat. The puncta could originate from several sources; while many may arise from intrinsic GABAergic Golgi type II local circuit neurons, these cells may not be the only or even the principal source. Thus, the dorsal division contains comparatively many immunopositive cells though fewer puncta than might be expected if the bulk of these were to arise from auditory thalamic interneurons. This suggests that other, extrinsic sources, such as the thalamic reticular nucleus, may be the source of such endings. A second point is that the form and density of the puncta is regionally specific within the medial geniculate complex. These local patterns might have a significant and regionally specific role in controlling the differential excitability of auditory thalamic neurons. The distribution of presumptive synaptic endings also has implications for the number and arrangement of glomeruli or synaptic nests. Thus, these circuit elements, which are common to the thalamic nuclei in other species, might play an important role in local synaptic circuits between different types of cells. If so, then the structural variations embodied in these patterns could subserve functional arrangements that differ among species. Such patterns might reflect concomitant physiological differences in the organization of local circuits within the microchiropteran medial geniculate body.
在髭蝠（Pteronotus parnellii）的内侧膝状体中，研究了对谷氨酸脱羧酶（GAD）或γ-氨基丁酸（GABA）呈免疫反应的神经元和轴突终末（斑点）的解剖结构和空间分布。主要发现如下：1）大多数GABA能神经元存在于背侧和腹侧部分，内侧部分即使有也很少；2）只有一小部分，约1%或更少的听觉丘脑神经元呈免疫阳性；3）免疫反应性斑点的密度与丘脑各部分GABA能神经元的数量无关，腹侧部分每单位面积的数量最多，内侧部分约为该值的75%，背侧部分仅约为50%；4）斑点的形态在每个部分都很独特，腹侧部分的斑点中等大小且相对简单，内侧部分的斑点主要较大、粗糙且复杂，而背侧部分的终末更细且更精致。这些模式在一些显著的例外情况下，重现了在大鼠和猫中发现的模式。斑点可能有多种来源；虽然许多可能来自内在的GABA能高尔基II型局部回路神经元，但这些细胞可能不是唯一的甚至不是主要来源。因此，背侧部分含有相对较多的免疫阳性细胞，但其斑点数量比如果这些细胞大部分来自听觉丘脑中间神经元所预期的要少。这表明其他外在来源，如丘脑网状核，可能是这些终末的来源。第二点是，斑点的形态和密度在内侧膝状体复合体中具有区域特异性。这些局部模式可能在控制听觉丘脑神经元的差异兴奋性方面具有重要的区域特异性作用。推测的突触终末的分布也对肾小球或突触巢的数量和排列有影响。因此，这些在其他物种的丘脑核中常见的回路元件，可能在不同类型细胞之间的局部突触回路中起重要作用。如果是这样，那么这些模式中体现的结构变化可能有助于不同物种之间不同的功能安排。这样的模式可能反映了小翼手目内侧膝状体中局部回路组织的伴随生理差异。
