Effects of conditioned running on plasma, liver and brain tryptophan and on brain 5‐hydroxytryptamine metabolism of the rat
British Journal of Pharmacology. 1985-09-01; 86(1): 33-41
DOI: 10.1111/j.1476-5381.1985.tb09432.x
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Chaouloff F, Elghozi JL, Guezennec Y, Laude D.
An investigation was made into the effects of conditioned running (1 h and 2 h at
20 m min-1), which accelerates lipolysis, on the concentrations of tryptophan
(Trp) in plasma, liver and brain and on 5-hydroxytrptamine (5-HT) and
5-hydroxyindoleacetic acid (5-HIAA) levels in brain. Running caused
time-dependent increases in plasma free Trp and brain Trp of the rat, leading to
increased brain 5-HT turnover as revealed by higher amounts of its metabolite,
5-HIAA. The ratio of brain Trp to plasma free Trp was decreased after 2 h of
running. Liver Trp content rose only after 3 h of running, while liver
unesterified fatty acid (UFA) concentrations remained unmodified. A comparison
between food deprivation and running (both of which promote lipolysis) was
performed. Running for 2 h affected to the same extent plasma Trp disposition
when compared with 24 h food deprivation. Nevertheless, the ratio of brain Trp to
plasma free Trp was decreased in the food-deprived rats, when compared to the
runners. Nicotinic acid, which inhibits fat catabolism, completely abolished the
plasma UFA increase induced by 1 h of running. The drug did not affect plasma
free Trp, brain Trp, 5-HT or 5-HIAA but enhanced plasma total Trp level.
Naloxone, an opiate antagonist, which decreased running-induced lipolysis, did
not alter plasma Trp disposition. Desipramine, an antidepressant compound,
affected only peripheral Trp concentrations of the runners. Plasma free and total
Trp concentrations were increased in desipramine-treated runners, compared with
saline-treated runners. In addition, desipramine increased the ratio of brain Trp
to plasma free Trp of the runners. Brain 5-HT and 5-HIAA were increased in both
desipramine-treated controls and runners. 9 The results suggest that running,
which like food deprivatiQn accelerates lipolysis, increases brain Trp content
and then 5-HT turnover. Comparison of these two physiological situations suggests
that effectiveness of brain Trp entry is much more altered by fasting.