Serotonin is an important neuromodulator involved in many physiological processes including mood and satiety. In the brain, serotonin is manufactured from tryptophan, as serotonin itself cannot cross the blood–brain barrier. Previous research has shown that blood-tryptophan levels increase upon ingestion of carbohydrates and decrease upon protein consumption. How this translates into serotonin availability is as yet under-researched. Therefore, we examined the effect of fasting versus consuming carbohydrates or protein on central serotonergic activity using a repeated-measures crossover design in a sample of 37 healthy men. The loudness dependence of auditory-evoked potentials (LDAEP) serves as a noninvasive method to study central serotonergic activity. Blood-glucose levels and mood changes were also monitored before and after the nutritional intervention. The intervention had a significant nutrition-specific effect on LDAEP and blood-glucose levels. A significant difference emerged between the fasting condition and satiety, with LDAEP being lower during satiety, irrespective of the type of food. Thus, this indicator of serotonergic activity increased after food consumption, which was further related to mood improvement. Moreover, the LDAEP differed between the 2 measurements only for the carbohydrate testing day, suggesting that LDAEP can be selectively modulated by the type of nutrition consumed. Our data further indicate a high intraindividual stability of LDAEP, as the electrophysiological signals were very similar in the fasting condition across the 2 testing days. Together, these findings demonstrate that the LDAEP can serve as a biological marker for central serotonergic activity, while at the same time being sensitive to nutritional changes.

血清素是一种重要的神经调节剂，涉及许多生理过程，包括情绪和饱腹感。在大脑中，血清素是由色氨酸制造的，因为血清素本身不能穿过血脑屏障。先前的研究表明，血液色氨酸水平在摄入碳水化合物时会增加，而在蛋白质消耗时会降低。这如何转化为血清素的可用性尚未得到充分研究。因此，我们在 37 名健康男性样本中使用重复测量交叉设计检查了禁食与摄入碳水化合物或蛋白质对中枢血清素活性的影响。听觉诱发电位的响度依赖性 (LDAEP) 作为一种非侵入性方法来研究中枢 5-羟色胺能活动。在营养干预前后也监测血糖水平和情绪变化。该干预措施对 LDAEP 和血糖水平具有显着的营养特异性影响。禁食状态和饱腹感之间出现了显着差异，无论食物类型如何，饱腹感期间 LDAEP 均较低。因此，食物消耗后血清素活性的这一指标增加，这进一步与情绪改善有关。此外，仅在碳水化合物测试日的 2 次测量之间的 LDAEP 不同，这表明 LDAEP 可以根据所消耗的营养类型进行选择性调节。我们的数据进一步表明 LDAEP 的高个体内稳定性，因为在 2 个测试日的禁食条件下电生理信号非常相似。一起，