Nie F, Wong-Riley M T
Department of Cellular Biology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
J Comp Neurol. 1995 May 22;356(1):115-31. doi: 10.1002/cne.903560108.
In the primate striate cortex, cytochrome oxidase (CO)-rich puffs differ from CO-poor interpuffs in their metabolic levels and physiological properties. The neurochemical basis for their metabolic and physiological differences is not well understood. The goal of the present study was to examine the relationship between the distribution of gamma aminobutyric acid (GABA)/non-GABA synapses and CO levels in postsynaptic neuronal profiles and to determine whether or not a difference existed between puffs and interpuffs. By combining CO histochemistry and postembedding GABA immunocytochemistry on the same ultrathin sections, the simultaneous distribution of the two markers in individual neuronal profiles was quantitatively analyzed. In both puffs and interpuffs, GABA-immunoreactive (GABA-IR) neurons were the only cell type that received both non-GABA-IR (presumed excitatory) and GABA-IR (presumed inhibitory) axosomatic synapses, and they had three times as many mitochondria darkly reactive for CO than non-GABA-IR neurons, which received only GABA-IR axosomatic synapses. GABA-IR neurons and terminals in puffs had a larger mean size, about twice as many darkly reactive mitochondria, and a higher ratio of non-GABA-IR to GABA-IR axosomatic synapses than those in interpuffs (2.3:1 vs. 1.6:1; P < 0.01). There were significantly more synapses of both non-GABA-IR and GABA-IR types in the neuropil of puffs than of interpuffs; however, the ratio of non-GABA-IR to GABA-IR synapses was significantly higher in puffs (2.86:1) than in interpuffs (2.08:1; P < 0.01). Our results are consistent with the hypothesis that the level of oxidative metabolism in postsynaptic neurons and neuronal processes is tightly governed by the strength and proportion of excitatory over inhibitory synapses. Thus, the present results suggest that (1) GABA-IR neurons in the macaque striate cortex have a higher level of oxidative metabolism than non-GABA ones because their somata receive direct excitatory synapses and their terminals are more tonically active; (2) the higher proportion of presumed excitatory synapses in puffs imposes a greater energy demand there than in interpuffs; and (3) excitatory synaptic activity may be more prominent in puffs than in interpuffs because puffs receive a greater proportion of excitatory synapses from multiple sources including the lateral geniculate nucleus, which is not known to project to the interpuffs.
在灵长类动物的纹状皮质中，富含细胞色素氧化酶（CO）的斑块与其周围CO含量较低的斑块在代谢水平和生理特性上存在差异。它们代谢和生理差异的神经化学基础尚未完全明确。本研究的目的是探讨γ-氨基丁酸（GABA）/非GABA突触分布与突触后神经元形态中CO水平之间的关系，并确定斑块和斑块间区域是否存在差异。通过在同一超薄切片上结合CO组织化学和包埋后GABA免疫细胞化学技术，对单个神经元形态中两种标记物的同时分布进行了定量分析。在斑块和斑块间区域中，GABA免疫反应性（GABA-IR）神经元是唯一既接受非GABA免疫反应性（推测为兴奋性）又接受GABA-IR（推测为抑制性）轴体突触的细胞类型，并且它们具有CO强反应性的线粒体数量是非GABA-IR神经元的三倍，后者仅接受GABA-IR轴体突触。斑块中的GABA-IR神经元和终末平均尺寸更大，CO强反应性线粒体数量约为斑块间区域的两倍，非GABA-IR轴体突触与GABA-IR轴体突触的比例更高（2.3:1 对 1.6:1；P < 0.01）。斑块的神经毡中，非GABA-IR和GABA-IR两种类型的突触数量均显著多于斑块间区域；然而，斑块中非GABA-IR突触与GABA-IR突触的比例（2.86:1）显著高于斑块间区域（2.08:1；P < 0.01）。我们的结果与以下假设一致，即突触后神经元和神经突中的氧化代谢水平受兴奋性突触与抑制性突触的强度和比例严格调控。因此，目前的结果表明：（1）猕猴纹状皮质中的GABA-IR神经元比非GABA神经元具有更高的氧化代谢水平，因为它们的胞体接受直接的兴奋性突触，且其终末更具紧张性活动；（2）斑块中推测的兴奋性突触比例较高，使其比斑块间区域需要更多的能量；（3）兴奋性突触活动在斑块中可能比在斑块间区域更显著，因为斑块从包括外侧膝状体核在内的多个来源接受了更大比例的兴奋性突触，而外侧膝状体核并不投射到斑块间区域。
