Gallagher Peter, Massey Anna E, Young Allan H, McAllister-Williams R Hamish
Stanley Research Centre, School of Neurology, Neurobiology and Psychiatry, University of Newcastle upon Tyne, NE1 4LP, UK.
BMC Psychiatry. 2003 Aug 4;3:10. doi: 10.1186/1471-244X-3-10.
Neurocognitive impairment is frequently described in a number of psychiatric disorders and may be a direct consequence of serotonergic dysfunction. As impairments in executive functions are some of the most frequently described, the purpose of this study was to examine the performance of normal volunteers on a range of executive tasks following a transient reduction of central serotonin (5-HT) levels using the method of acute tryptophan depletion (ATD).
Fifteen healthy male subjects participated in a within-subject, double-blind, counterbalanced crossover study. ATD was induced by ingestion of a 100 g amino-acid drink. Executive function was evaluated using the Wisconsin Card Sorting Test, Stroop, Verbal Fluency and Trail Making. Visual analogue scales were administered to assess mood.
Plasma free and total tryptophan concentrations were significantly reduced by the depleting drink (P < 0.001). ATD selectively improved motor speed/ attention on the Trails A test (P = 0.027), with no effect on subjective ratings of mood. Interaction effects between drink and the order of drink administration were observed on most neurocognitive tests.
The improvement in simple motor speed/ attention following ATD is in keeping with the ascribed role of 5-HT in the cortex, however performance on tests of executive function is not robustly altered. The presence of interaction effects on most tasks suggests that subtle changes may occur but are masked, possibly by simple learning effects, in the context of a crossover design. This has implications for the design of future studies, particularly those examining executive functions.
神经认知障碍在多种精神疾病中经常被描述，可能是血清素功能障碍的直接后果。由于执行功能障碍是最常被描述的症状之一，本研究的目的是通过急性色氨酸耗竭（ATD）方法，在中枢血清素（5-HT）水平短暂降低后，检查正常志愿者在一系列执行任务中的表现。
15名健康男性受试者参与了一项受试者内、双盲、平衡交叉研究。通过摄入100克氨基酸饮料诱导急性色氨酸耗竭。使用威斯康星卡片分类测试、斯特鲁普测试、语言流畅性测试和连线测试来评估执行功能。使用视觉模拟量表评估情绪。
耗竭饮料使血浆游离色氨酸和总色氨酸浓度显著降低（P < 0.001）。急性色氨酸耗竭选择性地提高了连线A测试中的运动速度/注意力（P = 0.027），对情绪的主观评分没有影响。在大多数神经认知测试中观察到饮料与饮料给药顺序之间的交互作用。
急性色氨酸耗竭后简单运动速度/注意力的改善与5-HT在皮质中的既定作用一致，然而执行功能测试的表现并没有显著改变。大多数任务中存在交互作用表明可能发生了细微变化，但在交叉设计的背景下可能被简单的学习效应掩盖了。这对未来研究的设计有影响，特别是那些检查执行功能的研究。
