rats fed the commercial chow had ( 1 ) a lower serum level of the six neutral amino acids ( valine , isoleucine leucine , tyrosine , phenylalanine , and methionine ) known to compete with tryptophan for its entry into the brain , ( 2 ) a higher ratio of tryptophan to the sum of the six neutral amino acids , ( 3 ) a lower ratio of tyrosine to the other five neutral amino acids , ( 4 ) a lower ratio of serotonin to 5-hydroxyindoleacetic acid in hypothalamus , ( 5 ) a higher tryptophan hydroxylase activity in raphe nuclei , and ( 6 ) a higher content of noradrenaline in hypothalamus .
C0006104
brain
C0423896
content