Central nervous system effects of caffeine and adenosine on fatigue.
Caffeine ingestion can delay fatigue during exercise, but the mechanisms remain elusive. This study was designed to test the hypothesis that blockade of central nervous system (CNS) adenosine receptors may explain the beneficial effect of caffeine on fatigue. Initial experiments were done to confirm an effect of CNS caffeine and/or the adenosine A(1)/A(2) receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) on spontaneous locomotor activity. Thirty minutes before measurement of spontaneous activity or treadmill running, male rats received caffeine, NECA, caffeine plus NECA, or vehicle during four sessions separated by approximately 1 wk. CNS caffeine and NECA (intracerebroventricular) were associated with increased and decreased spontaneous activity, respectively, but caffeine plus NECA did not block the reduction induced by NECA. CNS caffeine also increased run time to fatigue by 60% and NECA reduced it by 68% vs. vehicle. However, unlike the effects on spontaneous activity, pretreatment with caffeine was effective in blocking the decrease in run time by NECA. No differences were found after peripheral (intraperitoneal) drug administration. Results suggest that caffeine can delay fatigue through CNS mechanisms, at least in part by blocking adenosine receptors.
Davis
J Mark
JM
Department of Exercise Science, Schools of Public Health and Medicine, University of South Carolina, Columbia, South Carolina 29208, USA. jmdavis@sc.edu
Zhao
Zuowei
Z
Stock
Howard S
HS
Mehl
Kristen A
KA
Buggy
James
J
Hand
Gregory A
GA
D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects*; D005221:Fatigue / Q000188:drug therapy*; D007276:Injections, Intraventricular; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D018763:Muscle Fatigue / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D018047:Receptors, Purinergic P1 / Q000378:metabolism
D018047:Receptors, Purinergic P1; D019830:Adenosine-5'-(N-ethylcarboxamide); D002110:Caffeine