endogenous whole brain levels of dopamine , norepinephrine , serotonin , 5-hydroxyindoleacetic acid , tyrosine , phenylalanine , and tryptophan showed no tolerance to increased concentrations of brain catecholamines and indoleamines over the 5-week period , and no clear relation between the concentrations of these monoamines and the behavioral changes .
C0006104
brain
C0086045
concentrations