PHYSICAL EXERCISE – EVIDENCE FOR DIFFERENTIAL CONSEQUENCES OF TRYPTOPHAN ON 5-HT SYNTHESIS AND METABOLISM IN CENTRAL SEROTONERGIC CELL-BODIES AND TERMINALS
J. Neural Transmission. 1989-06-01; 78(2): 121-130
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1. J Neural Transm. 1989;78(2):121-30.
PHysical exercise: evidence for differential consequences of tryptophan on 5-HT
synthesis and metabolism in central serotonergic cell bodies and terminals.
Chaouloff F(1), Laude D, Elghozi JL.
(1)Laboratoire de Pharmacologie, INSERM U7, CHU Necker-E.M., Paris, France.
The aim of the present study was to investigate the effects of physical exercise
(running) on serotonin (5-hydroxytryptamine, 5-HT) synthesis and metabolism in
midbrain on the one hand, and in striatum and hippocampus on the other hand. To
address such a question, tryptophan (TRP) and 5-hydroxytryptophan (5-HTP) were
measured in running rats pretreated with an inhibitor of aromatic amino acid
decarboxylase, namely NSD 1015. In another series of experiments, the
consequences of a TRP load on TRP, 5-HT and 5-hydroxyindoleacetic acid (5-HIAA)
levels were compared in resting and running rats. Although running triggered a
30% increase in TRP levels in the three brain regions examined, inhibition of
5-HT synthesis by NSD 1015 was found to promote increased (midbrain), unchanged
(striatum) or decreased (hippocampus) 5-HTP accumulation in the running
situation, respectively compared to that measured in the resting situation.
Inasmuch as running-induced elevation in TRP was not associated with an increased
5-HTP accumulation in the striatum and the hippocampus, the consequences of
running on regional TRP, 5-HT and 5-HIAA levels were analyzed in saline- and
TRP-injected rats. Indeed, running, per se, was found to increase central TRP,
5-HT and 5-HIAA levels. On the other hand, a TRP load that promoted identical
increases in central TRP levels in running and resting rats revealed that
running, according to the region examined, differentially affected TRP
utilization in the 5-HT synthesis pathway. Thus, in the midbrains of the resting
and running rats, respective 210-250% increases in TRP led to identical 25%
increases in 5-HT and 90% increases in 5-HIAA levels. Conversely, in hippocampus,
TRP loads triggered marked increases in TRP levels that were similar in the
controls and the runners, but the rise in 5-HIAA promoted by such a precursor
load was found to be significantly minored in the runners, compared to the
resting rats. Moreover, such a running-induced impairment in 5-HT synthesis and
metabolism was even more observable in the striatum; thus, TRP loads which
promoted identical increases in striatal TRP levels in the resting and the
running rats respectively triggered a 50% and a 32% increase in 5-HT levels and a
76% and a 47% increase in 5-HIAA levels. The results presented herein indicate
that under certain pharmacological conditions, TRP utilization into the 5-HT
synthesis pathway is altered in serotonergic nerve terminals, but not in the cell
bodies of the running rat.
PMID: 2478662 [Indexed for MEDLINE]