Effect of acute and chronic exercise on plasma amino acids and prolactin concentrations and on [3H]ketanserin binding to serotonin2A receptors on human platelets.
The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has been shown to modulate various physiological and psychological functions such as fatigue. Altered regulation of the serotonergic system has been suggested to play a role in response to exercise stress. In the present study, the influence was investigated of acute endurance exercise and short-term increase in the amount of training on the concentrations of the 5-HT precursor tryptophan (TRP), of prolactin (PRL) and of branched-chain amino acids (BCAA) in the blood, as well as on the binding of [3H]ketanserin to the serotonin-2A (5-HT2A) receptors on platelets. Nine healthy endurance-trained men were tested the day before (I) and after (II) a 9-day training programme. Samples of venous blood were drawn after an overnight fast and following 5 h of cycling. Fasted and post-exercise plasma concentrations of free TRP, BCAA and free TRP:BCAA ratio did not differ between I and II. A significant decrease of plasma BCAA (P < 0.01) and significant augmentations of plasma free TRP, free TRP:BCAA ratio and PRL (P < 0.01) were found post-exercise. The increase in plasma PRL was smaller in II compared with I. Acute endurance exercise reduced the density of platelet 5-HT2A receptor [3H]ketanserin binding sites at I and II (P < 0.05). The basal density of the binding sites and the affinity of [3H]ketanserin for these binding sites were unaffected by an increase in the amount of training. The present results support the hypothesis that acute endurance exercise may increase 5-HT availability. This was reflected in the periphery by increased concentration of the 5-HT precursor free TRP, by increased plasma PRL concentration, and by a reduction of 5-HT2A receptors on platelets. It remains to be resolved whether these alterations in the periphery occur in parallel with an increase in the availability of 5-HT in the brain.
Strüder
H K
HK
Institute of Sports Games, German Sport University, Cologne.
Hollmann
W
W
Platen
P
P
Wöstmann
R
R
Weicker
H
H
Molderings
G J
GJ
D000328:Adult; D000596:Amino Acids / Q000097:blood*; D000597:Amino Acids, Branched-Chain / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007650:Ketanserin / Q000097:blood*; D008297:Male; D009994:Osmolar Concentration; D010807:Physical Endurance / Q000502:physiology; D011388:Prolactin / Q000097:blood*; D011985:Receptors, Serotonin / Q000097:blood*; D013997:Time Factors; D014316:Tritium; D014364:Tryptophan / Q000097:blood
D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D011985:Receptors, Serotonin; D014316:Tritium; D014364:Tryptophan; D011388:Prolactin; D007650:Ketanserin