QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fernstrom, J. D. Articles by Fernstrom, M. H. Search for Related Content PubMed PubMed Citation Articles by Fernstrom, J. D. Articles by Fernstrom, M. H.

---

Supplement: Branched-Chain Amino Acids in Exercise

Exercise, Serum Free Tryptophan, and Central Fatigue^1–3,

John D. Fernstrom^*,,4 and Madelyn H. Fernstrom^*,**,

Departments of ^* Psychiatry, Pharmacology, ^** Epidemiology, and Surgery, University of Pittsburgh School of Medicine, Pittsburgh PA 15213

⁴ To whom correspondence should be addressed. E-mail: fernstromjd{at}upmc.edu.

Brain tryptophan (TRP) concentrations and serotonin (5HT) synthesis and release increase during running. This increase in 5HT function may promote central fatigue and contribute to suboptimal physical performance. The rise in brain TRP is reputed to result from exercise-induced elevations in serum nonesterified fatty acid (NEFA) concentrations, which dissociate TRP from albumin in blood and increase the serum free TRP pool. But, as discussed in this article, ample evidence exists that the serum free TRP pool does not control brain TRP uptake. The clearest data are dietary, but pharmacologic data in exercising rats also support this conclusion. Changes in the serum levels of amino acids that compete with TRP for brain uptake appear also not to explain the rise in brain TRP. The mechanism is therefore not presently known. The link between the rise in brain TRP and 5HT synthesis/release is not simple: a rise in brain TRP stimulates 5HT synthesis/release in actively firing neurons. Hence, during exercise, only 5HT neurons that are firing should increase 5HT production/release when brain TRP rises. It is not known which 5HT neurons fire during exercise; the 5HT neurons that respond to exercise-induced increases in brain TRP are therefore not known. Hence, it is not possible to conclude which 5HT neurons contribute to the generation of central fatigue. Because some 5HT neurons control specific functions important to physical performance (e.g., respiration), the current understanding of 5HT neuronal function in central fatigue might benefit from the study of specific 5HT pathways during exercise.

KEY WORDS: • exercise • central fatigue • tryptophan • serotonin • brain

This article has been cited by other articles:

				B. Van Houdenhove, L. Verheyen, K. Pardaens, P. Luyten, and P. Van Wambeke Rehabilitation of decreased motor performance in patients with chronic fatigue syndrome: should we treat low effort capacity or reduced effort tolerance? Clinical Rehabilitation, December 1, 2007; 21(12): 1121 - 1142. [Abstract] [PDF]

				J. L. Ryan, J. K. Carroll, E. P. Ryan, K. M. Mustian, K. Fiscella, and G. R. Morrow Mechanisms of Cancer-Related Fatigue Oncologist, May 1, 2007; 12(suppl_1): 22 - 34. [Abstract] [Full Text] [PDF]