Effects of Phenylalanine, Phenylacetic Acid, Tyrosine, and Valine on Brain and Liver Serotonin in Rats

Abstract

Summary A study of the differential effects of excess dietary L-phenylalanine, L-tyrosine, L-valine, and phenylacetic acid on serotonin content of rat brain and liver indicated that phenylalanine is the most effective of these compounds. Five and 7% L-phenylalanine caused a decrease mainly in the brain. Seven percent tyrosine caused little or no change. Brain serotonin decreased when 6% L-valine was fed and brain and liver serotonin decreased when valine was included as 9% of the diet. Most of the change in liver serotonin is due to decreased food intake, since paired-fed control rats also showed decreased serotonin in this tissue. Phenylacetic acid caused an increase in brain serotonin, an effect opposite to that of phenylalanine or valine.