ADMINISTRATION OF A GABA(B) AGONIST BACLOFEN BEFORE RUNNING TO EXHAUSTION IN THE RAT - EFFECTS ON PERFORMANCE AND ON SOME INDICATORS OF FATIGUE

The present study was designed to examine the effects of administratio n of a GABAergic agonist (Baclofen) on run-time to exhaustion in train ed and untrained rats, and on some indicators of fatigue. Run-time to exhaustion on a treadmill set at a speed of 25 m . min(-1) was signifi cantly increased in both untrained (p < 0.01) and trained rats (p < 0. 005) administered with baclofen one hour before the exercise. The anim als who had run the longest time displayed the lowest concentrations o f liver and muscle glycogen, and a decrease in plasma glucose concentr ations (p < 0.05). The results of this investigation suggest that fati gue during prolonged exercise can be influenced by pharmacological adm inistration of a GABAergic agonist. Indicators of fatigue such as glyc emia, liver and muscular glycogen are not the limiting factors of perf ormance and central mechanisms play a key role at exhaustion.