Human tryptamine metabolism decreases during night sleep.

Fourteen healthy male volunteers took part in a study which aimed to determine whether utilization of tryptamine changes in relation to sleep and wakefulness. For this purpose urine samples were collected every 4 hr and urinary tryptamine and indoleacetic acid (IAA) were determined by fluorometric and spectrophotometric methods. Urinary concentration of IAA progressively increased during the day and fell during the night when subjects were asleep but not when subjects were awake. This evidence indicates that behavioral state rather than circadian variation determines the level of urinary IAA. Tryptamine (T) concentration also progressively increased during the day and continued to increase during the night. The mean log10 (IAA/T) ratio indicates that tryptamine metabolism decreases during the night when subjects are asleep. Therefore, human sleep may be associated with diminished activity of peripheral tryptamine.