Daily variations in in vivo tryptophan hydroxylation and in the contents of serotonin and 5-hydroxyindoleacetic acid in discrete brain areas of the rat.
The in vivo rate of brain tryptophan hydroxylation was determined through 5-hydroxytryptophan accumulation (5-HTPacc) following the administration of NSD 1015, a L-aromatic amino-acid decarboxylase inhibitor. This measurement was performed every 4 h throughout a 24 h hour period in 10 discrete brain areas of rats maintained on a regular 12 h/12 h light-dark cycle. The concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were also determined in untreated rats. Daily variations in 5-HTPacc were found in all the areas studied, the 5-HTPacc being higher during the dark period in most structures. These results strongly suggest that tryptophan hydroxylation is involved in the control of the 5-HT biosynthesis circadian rhythm. However, various patterns of 5-HT and 5-HIAA daily variations were observed, suggesting that the circadian factors affecting serotonin metabolism can be different among brain areas.
Poncet
L
L
Département de Médecine Expérimentale, INSERM U 52, CNRS URA 1195, Université Claude Bernard, Lyon, France.
Denoroy
L
L
Jouvet
M
M
D006916:5-Hydroxytryptophan / Q000378:metabolism; D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm / Q000502:physiology; D004563:Electrochemistry; D006834:Hydrazines / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism*; D006900:Hydroxylation; D007700:Kinetics; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D006834:Hydrazines; D009419:Nerve Tissue Proteins; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; C004297:3-hydroxybenzylhydrazine; D006916:5-Hydroxytryptophan; D001142:Aromatic-L-Amino-Acid Decarboxylases