Saito M, Kindel G, Karczmar A G, Rosenberg A
J Neurosci Res. 1986;15(2):197-204. doi: 10.1002/jnr.490150209.
In order to quantify the changes that occur in the cholinergic central nervous system with aging, we have compared acetylcholine (Ach) formation in brain cortex slice preparations from 2-year-old aged CBF-1 mouse brains and compared the findings with those in 2-4-month-old young adult mouse brain slices. Incorporation of exogenous radioactively labelled choline (31 nM [3H] choline) into acetyl choline in incubated brain slices was linear with time for 90 min. Percentage of total choline label distributed into Ach remained constant from 5 min after starting the incubation to 90 min. In contrast, distribution of label into intracellular free choline (Ch) and phosphorylcholine (Pch) changed continuously over this period suggesting that the Ch pool for Ach synthesis in brain cortex is different from that for Pch synthesis. Incorporation of radioactivity into Ach was not influenced by administration of 10 microM eserine, showing that the increment of radioactivity in Ach reflects rate of Ach formation, independently from degradation by acetylcholine esterases. Under our experimental conditions, slices from cortices of aged 24-month-old mouse brain showed a significantly greater (27%) incorporation of radioactivity into intracellular Ach than those from young, 2-4-month-old, brain cortices. Inhibitors of Ach release, 1 mM ATP or GABA, had no effect. Since concentration of radioactive precursor in the incubation medium was very low (31 nM), the Ch pool for Ach synthesis in slices was labelled without measurably changing the size of the endogenous pool. These data suggest a compensatory acceleration of Ach synthesis or else a smaller precursor pool specific for Ach synthesis into which labelled Ch migrated in aged brain.(ABSTRACT TRUNCATED AT 250 WORDS)
为了量化随着衰老胆碱能中枢神经系统发生的变化，我们比较了2岁龄CBF-1小鼠脑皮质切片制剂中乙酰胆碱（Ach）的生成，并将结果与2 - 4月龄年轻成年小鼠脑切片的结果进行比较。在孵育的脑切片中，外源性放射性标记胆碱（31 nM [³H]胆碱）掺入乙酰胆碱的过程在90分钟内与时间呈线性关系。从孵育开始5分钟到90分钟，分布到Ach中的总胆碱标记百分比保持恒定。相比之下，在此期间，标记物在细胞内游离胆碱（Ch）和磷酸胆碱（Pch）中的分布持续变化，这表明脑皮质中用于Ach合成的Ch池与用于Pch合成的不同。放射性掺入Ach不受10 microM毒扁豆碱给药的影响，表明Ach中放射性的增加反映了Ach的生成速率，与乙酰胆碱酯酶的降解无关。在我们的实验条件下，24月龄老龄小鼠脑皮质切片中放射性掺入细胞内Ach的量比2 - 4月龄年轻小鼠脑皮质切片显著高（27%）。Ach释放抑制剂1 mM ATP或GABA没有作用。由于孵育培养基中放射性前体的浓度非常低（31 nM），切片中用于Ach合成的Ch池被标记，而未显著改变内源性池的大小。这些数据表明Ach合成有代偿性加速，或者是衰老脑中有一个较小的、特定于Ach合成的前体池，标记的Ch迁移到其中。（摘要截断于250字）
