Sugden D, Namboodiri M A, Klein D C, Grady R K, Mefford I N
J Neurochem. 1985 Mar;44(3):769-72. doi: 10.1111/j.1471-4159.1985.tb12881.x.
L-5-Hydroxytryptophan (L-5-HTP) (20 or 200 mg/kg i.p.) but not L-tryptophan (500 mg/kg i.p.) loading substantially increases serum melatonin in sheep. In the present study we examined the effects of these compounds on pineal serotonin and six serotonin metabolites. L-Tryptophan failed to increase 5-hydroxytryptamine (5-HT; serotonin) or any of its metabolites despite a five-fold increase in pineal tryptophan. In contrast, L-5-HTP loading produced a marked increase in pineal 5-HT and its metabolites, including N-acetylserotonin (NAS) and melatonin, indicating that an increased synthesis of melatonin is responsible for the increased serum melatonin concentration after loading with this precursor. No change in pineal indoleamine N-acetyltransferase (NAT) activity was seen. These results are consistent with the suggestion that, during daytime in the sheep, 5-HT availability may limit the production of melatonin.
L-5-羟色氨酸（L-5-HTP）（腹腔注射20或200毫克/千克）而非L-色氨酸（腹腔注射500毫克/千克）负荷能显著提高绵羊血清褪黑素水平。在本研究中，我们检测了这些化合物对松果体5-羟色胺及六种5-羟色胺代谢产物的影响。尽管松果体色氨酸增加了五倍，但L-色氨酸未能提高5-羟色胺（5-HT；血清素）或其任何代谢产物的水平。相比之下，L-5-HTP负荷使松果体5-HT及其代谢产物（包括N-乙酰血清素（NAS）和褪黑素）显著增加，表明褪黑素合成增加是该前体负荷后血清褪黑素浓度升高的原因。松果体吲哚胺N-乙酰转移酶（NAT）活性未见变化。这些结果与以下观点一致：在绵羊白天时，5-HT的可利用性可能会限制褪黑素的产生。
