Kuhn E, Rysánek K, Brodan V, Spánková H
Experientia. 1976 Sep 15;32(9):1117-8. doi: 10.1007/BF01927577.
Prolonged sleep deprivation elicits a significant elevation of the plasma level of free tryptophan which appears to be involved in increased excretion of 5-HIAA during this state through enhanced 5-HT synthesis.