A comparison of D and L-tryptophan on the cerebral metabolism of 5-hydroxytryptamine and dopamine in the dog.
1 After D and L-tryptophan (50 mg/kg) were given intravenously in the dog, the concentration of the amino acid was increased in ventricular cerebrospinal fluid (CSF) during the subsequent 4 h or sampling, although the concentrations were significantly lower following the administration of the D-isomer. 2 There was no evidence that D-tryptophan increased the synthesis of 5-hydroxytryptamine (5-HT) in dog brain as judged by the failure to cause a change in 5-hydroxyindoleacetic acid (5-HIAA) concentrations in ventricular CSF different from that seen with controls. 3 There was no appreciable conversion of D-tryptophan to L-tryptophan in the dog. 4 D-tryptophan was cleared more rapidly from plasma than L-tryptophan. 5 No difference in plasma binding between D and L-tryptophan was detected.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004285:Dogs; D004298:Dopamine / Q000378:metabolism*; D006719:Homovanillic Acid / Q000134:cerebrospinal fluid; D006897:Hydroxyindoleacetic Acid / Q000134:cerebrospinal fluid; D007536:Isomerism; D008297:Male; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors; D014364:Tryptophan / Q000378:metabolism / Q000494:pharmacology*
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D004298:Dopamine; D006719:Homovanillic Acid