Effects of pyridoxine deficiency and DL-p-chlorophenylalanine administration to rats on 5-hydroxytryptamine and noradrenaline concentrations in brain and 5-hydroxytryptamine concentration in blood.
Pyridoxine deficiency in post-weanling rats caused a marked decrease in body weight and a small but significant decrease in brain weight. Although the concentration of circulating 5-hydroxytryptamine was markedly decreased, the concentrations of 5-hydroxytryptamine and noradrenaline in the brain were not affected. p-Chlorophenylalanine, an inhibitor of 5-hydroxytryptamine synthesis, decreased the 5-hydroxytryptamine content of brain to very low values in both the deficient and control animals, whereas the noradrenaline contents were not appreciably affected. The concentration of 5-hydroxytryptamine in blood, the origin of which is primarily gastrointestinal, was decreased only in the controls but not in the deficient animals after p-chlorophenylalanine treatment. These results suggest that whereas l-tryptophan hydroxylase (EC 1.14.3.2) is rate-limiting in the brain as has been reported by others, the pyridoxal 5'-phosphate-dependent enzyme 5-hydroxytryptophan decarboxylase (EC 4.1.1.28) may be more important in the gastrointestinal tract in the regulation of 5-hydroxytryptamine synthesis.
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry / Q000187:drug effects*; D002262:Carboxy-Lyases / Q000378:metabolism; D010134:Fenclonine / Q000494:pharmacology*; D006128:Growth / Q000187:drug effects; D008297:Male; D009638:Norepinephrine / Q000032:analysis*; D009929:Organ Size; D051381:Rats; D012701:Serotonin / Q000032:analysis* / Q000097:blood; D014365:Tryptophan Hydroxylase / Q000378:metabolism; D026681:Vitamin B 6 Deficiency / Q000378:metabolism*
D012701:Serotonin; D014365:Tryptophan Hydroxylase; D002262:Carboxy-Lyases; D010134:Fenclonine; D009638:Norepinephrine