A new metabolic pathway of L-threo-3,4-dihydroxyphenylserine, a precursor amino acid of norepinephrine, in the brain. Studies by in vivo microdialysis.
The metabolism and the effects of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) were studied in the rat brain striatum by in vivo microdialysis. In the brain L-threo-DOPS was metabolized by 3 different enzymes; aromatic L-amino acid decarboxylase, catechol-O-methyltransferase, and DOPS-aldolase. DOPS-aldolase was the main enzyme which metabolizes L-threo-DOPS. The amounts of the metabolites by L-amino acid decarboxylase (norepinephrine and its metabolites) were 0.4% of the total amounts of metabolites detected in the dialysate, while those by catechol-O-methyltransferase, 2.1%, and by DOPS-aldolase, 97.5%, after 100 min perfusion of L-threo-DOPS. L-threo-DOPS was found to increase extracellular levels of dopamine and serotonin, and to inhibit monoamine catabolism in the brain. Inhibition of DOPS-aldolase should improve its effectiveness as the supplement therapy of norepinephrine.
Maruyama
W
W
Department of Neurology, Nagoya University School of Medicine, Japan.
Nakahara
D
D
Naoi
M
M
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003342:Corpus Striatum / Q000378:metabolism; D015103:Droxidopa / Q000378:metabolism*; D007980:Levodopa / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D007980:Levodopa; D015103:Droxidopa; D009638:Norepinephrine