Biochemical and autoradiographic measurements of brain serotonin synthesis rate in the freely moving rat: a reexamination of the alpha-methyl-L-tryptophan method.
[en] Biochemical approaches were used in freely moving rats to determine, under steady-state conditions, the brain/arterial plasma partition coefficients of L-tryptophan and alpha-[3H]methyl-L-tryptophan, from which the lumped constant for the alpha-methyl-L-tryptophan method of estimating the rate of brain serotonin synthesis is calculated. The lumped constants were significantly different in the various structures examined: 0.149 +/- 0.003 in the raphe dorsalis, 0.103 +/- 0.002 in the raphe centralis, 0.087 +/- 0.003 in the reticular formation, and 0.62 +/- 0.08 in the pineal gland. From these data we proposed a two-compartment model to calculate the rate of serotonin synthesis by quantitative autoradiography using a three-time point experiment. Rates of synthesis for the raphe dorsalis and the reticular formation (620 +/- 57 and 80 +/- 35 pmol/g of tissue/min, respectively) were similar to those measured simultaneously by biochemical means, but rates were 50% higher for the raphe centralis (568 +/- 90 vs. 381 +/- 31 pmol/g of tissue/min). The lack of dynamic equilibrium of the tracer between plasma and tissue pools may explain the discrepancy between the two methods. Our findings did not confirm previous data, indicating that the application of the autoradiographic method to measure the rate of brain serotonin synthesis using alpha-methyl-L-tryptophan as tracer has limitations.
Research center :
GIGA CRC (Cyclotron Research Center) In vivo Imaging-Aging & Memory - ULiège
Disciplines :
Radiology, nuclear medicine & imaging
Author, co-author :
Gharib, Abdallah
Balende, Cédar
Sarda, Nicole
Weissmann, Dinah
Plenevaux, Alain ; Université de Liège - ULiège > Centre de recherches du cyclotron
Luxen, André ; Université de Liège - ULiège > Département de chimie (sciences) > Chimie organique de synthèse - Centre de recherches du cyclotron
Bobillier, Pierre
Pujol, Jean-François
Language :
English
Title :
Biochemical and autoradiographic measurements of brain serotonin synthesis rate in the freely moving rat: a reexamination of the alpha-methyl-L-tryptophan method.
Publication date :
1999
Journal title :
Journal of Neurochemistry
ISSN :
0022-3042
eISSN :
1471-4159
Publisher :
Blackwell Science, Oxford, United Kingdom
Volume :
72
Issue :
6
Pages :
2593-600
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
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