Possible role of octopamine and tyramine in the antihypertensive and antidepressant effects of tyrosine.
The administration of a dose of 200 mg/kg of tyrosine (as either the free amino acid or the ethyl ester) increased the 24-hour excretion of p-hydroxyphenethyleneglycol (p-HPG) and p-hydroxyphenylethanol, metabolites of octopamine and tyramine, by 147 and 50%, respectively. One hour after this dose of tyrosine, brain levels of p-HPG and p-hydroxyphenylacetic acid (p-HPA), another metabolite of tyramine, were increased by 82 and 196%, respectively. Pretreatment with Ro4-4602, a peripheral decarboxylase inhibitor, reduced by 50% the tyrosine-induced increases in brain p-HPA levels, suggesting that tyramine was partially formed in the brain parenchyma. Tyrosine caused only slight, but non-significant increases in brain levels of catecholamine metabolites. These results suggest that tyrosine-induced increases in the production of tyramine and octopamine in brain may account for some of the effects of tyrosine, such as its antihypertensive and reported antidepressant properties.
D000818:Animals; D001545:Benserazide / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D000431:Ethanol / Q000031:analogs & derivatives*; D005026:Ethylene Glycols / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D008297:Male; D009655:Octopamine / Q000378:metabolism*; D010636:Phenols; D010648:Phenylacetates / Q000378:metabolism*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014439:Tyramine / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism* / Q000494:pharmacology
D005026:Ethylene Glycols; D010636:Phenols; D010648:Phenylacetates; D009655:Octopamine; C011867:4-hydroxyphenylethanol; C034604:4-hydroxyphenethylene glycol; C008070:4-hydroxyphenylacetic acid; D000431:Ethanol; D014443:Tyrosine; D001545:Benserazide; D010626:Phenylethyl Alcohol; D014439:Tyramine