Kohno Y
Nihon Yakurigaku Zasshi. 1981 Mar;77(3):281-93.
Changes in tryptophan (Trp) concentrations in the peripheral and brain tissues and their influences on brain serotonin (5-HT) metabolism were investigated after i.p. administrations of L-DOPA alone and in combination with Ro4-4602 in male Wistar rats. L-DOPA alone elicited marked increases of both plasma free and liver Trp levels, and a slight increase of brain Trp level. Concomitant application of L-DOPA and Ro4-4602 did not change peripheral Trp concentrations but did reduce brain Trp level. Brain 5-HT levels were reduced in proportion to the increase of dopamine (DA) level by L-DOPA alone and Ro4-4602 plus L-DOPA. A marked increase of 5-HIAA level was exhibited by L-DOPA alone, while Ro4-4602 plus L-DOPA increased 5-HIAA levels slightly despite a marked decrease in 5-HT levels. The decrease of 5-HT and increase of 5-HIAA levels were also observed after administration of L-DOPA to neonatal rats in which the brain tryptophan hydroxylase was considered to be saturated. These results suggest that changes in 5-HT metabolism after L-DOPA injections are not only caused by DA which displaces 5-HT from vesicular stores, but also by changes in Trp concentrations in the plasma and brain which alter 5-HT synthesis and turnover.
在雄性Wistar大鼠腹腔注射左旋多巴（L-DOPA）单独给药以及与Ro4-4602联合给药后，研究了外周和脑组织中色氨酸（Trp）浓度的变化及其对脑血清素（5-HT）代谢的影响。单独使用L-DOPA可使血浆游离Trp水平和肝脏Trp水平显著升高，脑Trp水平略有升高。同时应用L-DOPA和Ro4-4602不会改变外周Trp浓度，但会降低脑Trp水平。单独使用L-DOPA以及Ro4-4602加L-DOPA时，脑5-HT水平会随着多巴胺（DA）水平的升高而相应降低。单独使用L-DOPA可使5-HIAA水平显著升高，而Ro4-4602加L-DOPA尽管5-HT水平显著降低，但5-HIAA水平略有升高。在给脑色氨酸羟化酶被认为已饱和的新生大鼠注射L-DOPA后，也观察到了5-HT的降低和5-HIAA水平的升高。这些结果表明，L-DOPA注射后5-HT代谢的变化不仅是由DA从囊泡储存中置换5-HT引起的，还与血浆和脑中Trp浓度的变化有关，这些变化会改变5-HT的合成和周转。
