in the rat , administration of 3- ( 3,4-dihydroxy ) -l-phenylalanine ( l-dopa ) simultaneously with the corresponding alpha-keto acid , 3,4-dihydroxyphenylpyruvic acid ( dhppa ) , gives significantly higher concentrations of l-dopa in the serum and of dopamine and homovanillic acid in the brain than the same dose of l-dopa alone .
C0086045
concentrations
C0006104
brain