Dose-response decrease in plasma tryptophan and in brain tryptophan and serotonin after tryptophan-free amino acid mixtures in rats.
Rats fasted 15 hours were treated p.o. with increasing amounts (660 and 1320 mg/kg body weight) of a mixture containing a fixed proportion of seven essential amino acids (L-phenylalanine 13.6%, L-leucine 6.0%, L-isoleucine 12.1%, L-methionine 12.1%, L-lysine 30.3%, L-threonine 10.6%, L-valine 15.2%) and lacking tryptophan. The mixtures produced a dose-response decrease of free (by 34% after the lower dose and by 58% after the higher dose of the mixture) and total (by 10 and 31%) plasma tryptophan and of brain tryptophan (by 38 and 65%), serotonin (by 17 and 41%) and 5-hydroxyindole acetic acid (by 21 and 49%). The mechanisms of these changes are discussed.
Moja
E A
EA
Chair of Psychobiology, Medical School, University of Modena, Italy.
Cipolla
P
P
Castoldi
D
D
Tofanetti
O
O
D000596:Amino Acids / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000097:blood* / Q000378:metabolism
D000596:Amino Acids; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan