Jacoby J H, Thomas R F, Poulakos J J, Siegel A
Naunyn Schmiedebergs Arch Pharmacol. 1979 Jun;307(2):143-9. doi: 10.1007/BF00498456.
The elevation of brain tryptophan, 5-hydroxytryptophan and 5-hydroxyindoles (serotonin + 5-hydroxyindole acetic acid) that results from a tryptophan load is potentiated by prior administration of methiothepin, a serotonin receptor antagonist. Co-administration of valine with tryptophan attenuates these effects even in animals receiving methiothepin pretreatment. Administration of methiothepin and tryptophan to rats with widespread reduction of brain 5-hydroxyindole levels resulting from raphe lesions or 5,7-dihydroxytryptamine pretreatment still enabled brain tryptophan levels to rise considerably above the sum of increases found in animals receiving one or the other. Following transection of the spinal cord, the cranial portion still exhibited enhanced uptake of tryptophan and 5-hydroxyindole synthesis following methiothepin plus tryptophan treatment, however, both these events were absent in the caudal segment. Apparently, enhanced tryptophan uptake can proceed in the presence of minimal neuronal activity; however, when nerve impulse flow is eliminated, both 5-hydroxyindole synthesis and tryptophan uptake is impaired.
色氨酸负荷导致的脑内色氨酸、5-羟色氨酸和5-羟吲哚（血清素+5-羟吲哚乙酸）水平升高，会因预先给予5-羟色胺受体拮抗剂甲硫哒嗪而增强。即使在接受甲硫哒嗪预处理的动物中，缬氨酸与色氨酸共同给药也会减弱这些作用。对因中缝核损伤或5,7-二羟色胺预处理导致脑内5-羟吲哚水平广泛降低的大鼠给予甲硫哒嗪和色氨酸，仍能使脑内色氨酸水平大幅升高，高于单独给予其中一种药物的动物的升高总和。脊髓横断后，脑颅部分在甲硫哒嗪加色氨酸处理后仍表现出增强的色氨酸摄取和5-羟吲哚合成，然而，尾段均未出现这些情况。显然，在神经元活动极少的情况下，色氨酸摄取增强仍可进行；然而，当神经冲动流被消除时，5-羟吲哚合成和色氨酸摄取均受损。
