Scarnà A, McTavish S F B, Cowen P J, Goodwin G M, Rogers R D
University Department of Psychiatry, Warneford Hospital, Oxford, OX37JX, UK.
Psychopharmacology (Berl). 2005 Jun;179(4):761-8. doi: 10.1007/s00213-004-2105-2. Epub 2005 Feb 5.
We have previously shown that a 60-g mixture of branched chain amino acids (BCAAs) lowers the plasma availability of the catecholamine precursors tyrosine (TYR) and phenylalanine (PHE) and produces biochemical and neuropsychological changes consistent with impaired dopamine neurotransmission. However, the BCAA mixture also lowers the ratio of tryptophan (TRP) to BCAA which could impair brain serotonin function.
To determine the biochemical and neuropsychological effects of a BCAA mixture supplemented with TRP.
We studied 32 healthy volunteers who were randomly and blindly allocated to either a single administration of amino acid mixture (60 g BCAA and 2 g TRP) or placebo. We carried out venous sampling to measure plasma levels of amino acids and performed selected cognitive tasks sensitive to monoamine manipulation 5 h after mixture ingestion.
Relative to placebo, the BCAA/TRP mixture substantially lowered the ratio of TYR+PHE:BCAA and increased plasma prolactin. The ratio of TRP:BCAA was also lowered but to a lesser extent. The BCAA/TRP mixture produced significant changes in a task of decision-making where volunteers showed reduced discrimination between gambles with large and small losses.
A 62 g BCAA/TRP mixture decreases the availability of TYR and PHE for brain catecholamine synthesis and increases plasma prolactin consistent with lowered brain dopamine function. Addition of 2 g TRP to the 60 g BCAA mixture does not prevent a reduction of the ratio TRP:BCAA relative to placebo. The effects of the BCAA/TRP mixture on decision-making suggest a general action of dopamine pathways on the processing of emotional information in risky choice, including punishment-related cues, consistent with suggestions that dopamine mechanisms mediate behavioural responses to aversive as well as appetitive stimuli in instrumental conditioning.
我们之前已经表明，60克支链氨基酸（BCAAs）混合物可降低儿茶酚胺前体酪氨酸（TYR）和苯丙氨酸（PHE）的血浆可用性，并产生与多巴胺神经传递受损一致的生化和神经心理学变化。然而，BCAA混合物也会降低色氨酸（TRP）与BCAA的比例，这可能会损害大脑血清素功能。
确定补充TRP的BCAA混合物的生化和神经心理学作用。
我们研究了32名健康志愿者，他们被随机且盲法分配至单次给予氨基酸混合物（60克BCAA和2克TRP）或安慰剂组。我们进行静脉采样以测量血浆氨基酸水平，并在摄入混合物5小时后进行对单胺操作敏感的特定认知任务。
相对于安慰剂，BCAA/TRP混合物大幅降低了TYR+PHE:BCAA的比例，并增加了血浆催乳素。TRP:BCAA的比例也有所降低，但程度较小。BCAA/TRP混合物在一项决策任务中产生了显著变化，志愿者在该任务中对大小损失的赌博之间的辨别能力降低。
62克BCAA/TRP混合物降低了大脑儿茶酚胺合成中TYR和PHE的可用性，并增加了血浆催乳素，这与大脑多巴胺功能降低一致。在60克BCAA混合物中添加2克TRP并不能阻止相对于安慰剂而言TRP:BCAA比例的降低。BCAA/TRP混合物对决策的影响表明多巴胺通路在风险选择中对情绪信息处理（包括与惩罚相关的线索）具有普遍作用，这与多巴胺机制介导工具性条件反射中对厌恶和奖励刺激的行为反应的观点一致。
