by the use of the brain micro-dialysis technique combined with hplc , the changes in the extracellular levels of dopamine ( da ) and its metabolites , 3,4-dihydroxyphenylacetic acid ( dopac ) and homovanillic acid ( hva ) , and a serotonin ( 5-ht ) metabolite , 5-hydroxyindoleacetic acid ( 5-hiaa ) were examined in the rat striatum before and after intracerebral injection of a vehicle or ( 6r ) -l-erythro-tetrahydrobiopterin ( 6r-bh ( 4 ) ) , the natural form of the cofactor for the tryrosine hydroxylase and tryptophan hydroxylase .
C0020364
hydroxylase
C0041252
tryptophan hydroxylase