Effects of conditioned running on plasma, liver and brain tryptophan and on brain 5‐hydroxytryptamine metabolism of the rat

F. Chaouloff, J.L. Elghozi, Y. Guezennec, D. Laude
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.

 

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