Table 2

Plasma total and free tryptophan in male and female subjects before and after depletion

Plasma tryptophanPlasma tryptophan conc., nmol⋅ml−1
Male subjects Female subjects
BeforeAfterBeforeAfter
Free*12 ± 63.4 ± 3.06.1 ± 1.8 0.66 ± 0.32
Total64 ± 1611 ± 652 ± 167.8 ± 4.6
  • Data are presented as the mean ± SD with seven subjects of each sex. All subjects were scanned before and after plasma tryptophan depletion. 

  • * The plasma free tryptophan in male subjects was significantly different (P < 0.05; ANOVA) from that in female subjects at the baseline, but not after ATD. There was no significant correlation (P > 0.05; Pearson rank correlation) between plasma free tryptophan levels and rate of serotonin synthesis shown in Table 1

  • No significant difference (P > 0.05; ANOVA) between plasma total tryptophan levels at the baseline or after ATD in male and female subjects. There was no significant correlation between plasma total tryptophan levels and the serotonin synthesis rates shown in Table 1