4-Methoxy-3,5-dihydroxyphenylalanine

According to Thoenen et al. [249], 5-hydroxy dopa gives rise to marked norepinephrine depletion in the cat. Its 0-methyl derivative, 4-methoxy-3,5-dihydroxyphenylalanine, exerts a hypotensive effects in animals [245,250]. 

More recently a number of related amino acids have been tested as possible precursors for the formation of false adrenergic transmitters. Among these compounds the amino acids 5-hydroxyDOPA and its methoxylated derivative 4-methoxy, 3,5-dihydroxyphenylalanine (Fig. 11) have proved of interest. These compounds give rise to the corresponding decarboxylated and ) -hydroxylated amines which are stored in the adrenergic nerves. There is, however, some tissue selectivity with a much larger proportion of the NA in peripheral sympathetic nerves being replaced by the false amines than in the CNS, presumably because the parent amino acids enter the brain only slowly. 

DA = dopamine DOPA = dihydroxyphenylalanine MHPG = 3-methoxy-4-hydroxyphenylglycol. 

A, adrenaline COMT, catechol-O-methyl transferase CSF, cerebrospinal fluid DA, 3,4-dihydroxyphenylethylamine (dopamine) Dopa, 3,4-dihydroxyphenylalanine 5HIAA, 5-hydroxyindoleacetic acid 5HT, 5-hydroxytryptamine (serotonin) 5HTP, 5-hydroxytryptophan HVA, 3-methoxy-4-hydroxyphenylacetic acid (homovanillic acid) MAO, monoamine oxidase MAOI, monoamine oxidase inhibitor MHPG,... 

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