Effect of a Tryptophan Deficient Diet on Brain Serotonin and Plasma Tryptophan Level.

One hundred and eight female Wistar rats were placed on tryptophan sufficient or tryptophan deficient diets. Six animals from each group were sacrificed after 2 days, 4 days and multiples of 4 days. Plasma tryptophan level was found to reflect changes in brain serotonin level. Furthermore, plasma tryptophan and brain serotonin were significantly decreased after as little as 4 days on the tryptophan deficient diet. The levels of plasma tryptophan and brain serotonin were relatively constant from 4 to 28 days, at which time both showed further decreases.