Melatonin counteracts the 5-aminolevulinic acid-induced rise of rat forebrain tryptophan and serotonin concentrations at night.
When rats were exposed to extended light into the normal dark phase, the administration of 5-aminolevulinic acid (5-ALA) markedly stimulated the accumulation of tryptophan (TRP) and the synthesis of serotonin (5-HT) in the forebrain. When a single injection of melatonin (25 micrograms) was given near the end of the 5-ALA treatment, the rise in forebrain TRP levels was either totally prevented or reversed; likewise, the increased levels of 5-HT were also suppressed. Melatonin by itself also slightly suppressed forebrain TRP levels in non-5-ALA-treated rats. Whether these are pharmacological or physiological effects of melatonin remains to be determined.
Daya
S
S
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
Nonaka
K O
KO
Reiter
R J
RJ
D000622:Aminolevulinic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002940:Circadian Rhythm / Q000187:drug effects*; D003624:Darkness; D007982:Levulinic Acids / Q000494:pharmacology*; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*
D007982:Levulinic Acids; D012701:Serotonin; D000622:Aminolevulinic Acid; D014364:Tryptophan; D008550:Melatonin