Mora F, Myers R D
Brain Res Bull. 1984 Sep;13(3):421-6. doi: 10.1016/0361-9230(84)90092-3.
Rats were surgically prepared with two sets of guide cannulae positioned bilaterally to rest below the superficial layer of the prefrontal, parietal and occipital regions of the cerebral cortex. Following post-operative recovery, two cortical sites were labeled simultaneously by microinjection of a 1.0 microliter volume of 5.0 microCi of D-[U-14C]-glucose. After a 20 min interval for incorporation into amino acids, two sites were concurrently perfused over an interval of 20 min by means of a push-pull cannula system with an artificial CSF solution at a rate of 25 microliters/min. A thin-layer chromatographic assay for separation of amino acid neurotransmitters was used to estimate the content in each sample of perfusate of labeled gamma-amino-butyric acid (GABA), glutamate, glutamine, aspartate and glycine. The results show that recovery of three amino acids, GABA, aspartate and glycine, was uniform among the three areas of the rat's cortex. However, the synthesis of labeled glutamate and glutamine was significantly lower within the parietal cortex in comparison to that of the prefrontal and occipital regions. Overall, the recovery of GABA was proportionally higher whereas glycine was lower than that of the other amino acids. The difference in the results from previous observations can be attributed to the distribution of amino acids in neurons and their terminals in deeper layers of cortex, which may give a different profile of release when epidural measurements are obtained.
通过手术给大鼠双侧植入两组引导套管，使其位于大脑皮层前额叶、顶叶和枕叶区域表层下方。术后恢复后，通过微量注射1.0微升含5.0微居里D-[U-14C]-葡萄糖的溶液，同时标记两个皮层位点。在经过20分钟使其掺入氨基酸的间隔后，通过推挽式套管系统，以25微升/分钟的速率用人工脑脊液溶液在20分钟的间隔内同时灌注两个位点。采用用于分离氨基酸神经递质的薄层色谱分析法，来估算每个灌注液样本中标记的γ-氨基丁酸（GABA）、谷氨酸、谷氨酰胺、天冬氨酸和甘氨酸的含量。结果显示，GABA、天冬氨酸和甘氨酸这三种氨基酸在大鼠皮层的三个区域中的回收情况是一致的。然而，与前额叶和枕叶区域相比，顶叶皮层内标记的谷氨酸和谷氨酰胺的合成显著较低。总体而言，GABA的回收比例较高，而甘氨酸的回收比例低于其他氨基酸。先前观察结果的差异可归因于氨基酸在皮层深层神经元及其终末中的分布情况，这在进行硬膜外测量时可能会呈现出不同的释放情况。
