Effects of conditioned running on plasma, liver and brain tryptophan and on brain 5-hydroxytryptamine metabolism of the rat.
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.
Chaouloff
F
F
Elghozi
J L
JL
Guezennec
Y
Y
Laude
D
D
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003216:Conditioning, Operant; D003891:Desipramine / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009525:Niacin / Q000494:pharmacology; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D012420:Running; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors; D014364:Tryptophan / Q000097:blood / Q000378:metabolism*; D014633:Valine / Q000494:pharmacology
D009525:Niacin; D012701:Serotonin; D009270:Naloxone; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D014633:Valine; D003891:Desipramine