Lee I S, Renno W M, Beitz A J
Department of Anatomy College of Veterinary Medicine, Seoul National University, South Korea.
J Comp Neurol. 1992 Jul 1;321(1):65-82. doi: 10.1002/cne.903210107.
Taurine has been proposed as an inhibitory neurotransmitter or neuromodulator in the vertebrate central nervous system. Within the spinal cord, taurine has been shown to have a direct inhibitory effect on spinal neurons and to have a selective antinociceptive effect on chemically induced nociception. Although sufficient data exists to suggest that taurine plays a neurotransmitter or neuromodulatory role in the spinal cord, it is not known whether this amino acid is present in axon terminals nor if this amino acid has a unique pattern of distribution within spinal tissue. To address these questions a monoclonal antibody against taurine was employed to localize taurine-like immunoreactivity in the dorsal horn of the rat spinal cord by using both light and electron microscopic techniques. Taurine-like immunoreactivity was most dense and most prominent in laminae I and II of the dorsal horn. A moderate amount of immunoreactivity was also present in laminae VIII and IX and X while the remaining laminae were only lightly stained. In laminae I and II taurine-like immunostaining was evident within neuronal cell bodies, dendrites, myelinated and unmyelinated axons, axon terminals, and astrocytes and their processes. Cell counts of these two laminae indicated that approximately 30% of neuronal perikarya at the C2 level, 52% of neuronal perikarya at the T6 level, and 18% of neuronal perikarya at the L2 level of the cord exhibited taurine-like immunoreactivity. With preembedding diaminobenzidine staining, approximately 20% of the axons examined in laminae I and II were found to be immunoreactive for taurine. Using postembedding immunogold staining in combination with quantitative procedures, the highest densities of gold particles were found in axon terminals containing pleomorphic vesicles and forming symmetrical synapses (36.8 particles/micron2), in a subpopulation of myelinated axons (34.2 particles/micron2), in a subpopulation of neuronal dendrites (32.6 particles/micron2), and in capillary endothelial cells (39.8 particles/micron2). Moderate labeling occurred in astrocytes (20.9 particles/micron2) and neuronal perikarya (18.7 particles/micron2). The localization of taurine to presumptive inhibitory axon terminals provides anatomical support for the hypothesis that taurine may serve an inhibitory neurotransmitter role in the superficial dorsal horn of the spinal cord. On the other hand, its localization to astrocytes and endothelial cells within both the dorsal ventral horns implies that it serves other nonneuronal functions as well.
牛磺酸已被提出作为脊椎动物中枢神经系统中的一种抑制性神经递质或神经调质。在脊髓内，牛磺酸已被证明对脊髓神经元具有直接抑制作用，并对化学诱导的伤害感受具有选择性抗伤害感受作用。尽管有足够的数据表明牛磺酸在脊髓中发挥神经递质或神经调节作用，但尚不清楚这种氨基酸是否存在于轴突终末，也不清楚这种氨基酸在脊髓组织内是否具有独特的分布模式。为了解决这些问题，通过使用光学和电子显微镜技术，采用一种针对牛磺酸的单克隆抗体来定位大鼠脊髓背角中的牛磺酸样免疫反应性。牛磺酸样免疫反应性在背角的I层和II层中最为密集和显著。在VIII层、IX层和X层中也存在适量的免疫反应性，而其余层仅轻度染色。在I层和II层中，牛磺酸样免疫染色在神经元细胞体、树突、有髓和无髓轴突、轴突终末、星形胶质细胞及其突起内均很明显。对这两层的细胞计数表明，在脊髓C2水平约30%的神经元胞体、T6水平52%的神经元胞体以及L2水平18%的神经元胞体表现出牛磺酸样免疫反应性。通过预包埋二氨基联苯胺染色，发现在I层和II层中检查的约20%的轴突对牛磺酸具有免疫反应性。使用包埋后免疫金染色结合定量程序，在含有多形性囊泡并形成对称突触的轴突终末（36.8个颗粒/微米²）、有髓轴突亚群（34.2个颗粒/微米²）、神经元树突亚群（32.6个颗粒/微米²）以及毛细血管内皮细胞（39.8个颗粒/微米²）中发现了最高密度的金颗粒。在星形胶质细胞（20.9个颗粒/微米²）和神经元胞体（18.7个颗粒/微米²）中出现中等程度的标记。牛磺酸在假定的抑制性轴突终末的定位为牛磺酸可能在脊髓浅表背角中发挥抑制性神经递质作用的假说提供了解剖学支持。另一方面，它在背腹角内的星形胶质细胞和内皮细胞中的定位意味着它也发挥其他非神经元功能。
