Ohue T, Koshimura K, Akiyama Y, Watanabe Y, Miwa S
Department of Pharmacology, Kyoto University Faculty of Medicine, Japan.
Brain Res. 1992 Jan 20;570(1-2):173-9. doi: 10.1016/0006-8993(92)90579-x.
Recently, we reported that intracerebroventricular administration of 6R-L-erythro-tetrahydrobiopterin (6R-BH4), a common natural cofactor for phenylalanine, tyrosine and tryptophan hydroxylases, enhances in vivo exocytotic release of acetylcholine (ACh) from the rat hippocampus, as monitored by brain microdialysis. In the present study, we developed a method for separation of ACh from 6R-BH4 on small columns of Sephadex G-10, which allowed us to determine by high pressure liquid chromatography (HPLC) the changes of ACh levels recovered in dialysates following addition of 6R-BH4 to the dialyzing fluid. Infusions of 6R-BH4 (final concentration, 0.25, 0.5 and 1 mM in the perfusing fluid) produced concentration-dependent increases in ACh levels in dialysates (1.5-, 3- and 8-fold of the basal levels, respectively), but was without effect on choline levels in dialysates. Infusion of 6S-L-erythro-5,6,7,8-tetrahydrobiopterin (6S-BH4), an unnatural diastereoisomer of 6R-BH4, or L-erythro-biopterin (biopterin), an oxidized form of 6R-BH4, did not affect the ACh levels in dialysates. The 6R-BH4-induced increase in ACh levels persisted after pretreatment with atropine, a muscarinic antagonist, but did not occur in rats pretreated with reserpine to deplete monoamines. These results show that 6R-BH4 stimulates exocytotic ACh release in the hippocampus through action on a local monoaminergic system in the hippocampus.
最近，我们报道称，通过脑微透析监测发现，向脑室内注射6R-L-赤藓糖型四氢生物蝶呤（6R-BH4），一种苯丙氨酸、酪氨酸和色氨酸羟化酶的常见天然辅因子，可增强大鼠海马体内乙酰胆碱（ACh）的胞吐释放。在本研究中，我们开发了一种在Sephadex G-10小柱上分离ACh与6R-BH4的方法，这使我们能够通过高压液相色谱（HPLC）测定在透析液中添加6R-BH4后回收的ACh水平变化。输注6R-BH4（灌注液中的终浓度为0.25、0.5和1 mM）使透析液中的ACh水平呈浓度依赖性增加（分别为基础水平的1.5倍、3倍和8倍），但对透析液中的胆碱水平无影响。输注6S-L-赤藓糖型5,6,7,8-四氢生物蝶呤（6S-BH4），6R-BH4的非天然非对映异构体，或L-赤藓糖型生物蝶呤（生物蝶呤），6R-BH4的氧化形式，均不影响透析液中的ACh水平。用毒蕈碱拮抗剂阿托品预处理后，6R-BH4诱导的ACh水平升高仍然存在，但在用利血平预处理以耗尽单胺类物质的大鼠中未出现这种情况。这些结果表明，6R-BH4通过作用于海马体中的局部单胺能系统刺激海马体中ACh的胞吐释放。
