changes in the activity of neurotransmitters in dementia were studied by measuring the activities of each of choline acetyltransferase ( cat ) , dopamine-beta-hydroxylase ( dbh ) and hydroxylase cofactor ( tetrahydrobiopterine ; bph4 ) , and the concentrations of homovanillic acid ( hva ) and vasopressin .
C0013032
dopamine-beta-hydroxylase
C0020364
hydroxylase