Endurance training increases acetylcholine receptor quantity at neuromuscular junctions of adult rat skeletal muscle

THE aim of the study was to test the hypothesis that a 16 week endurance tr aining program would alter the abundance of endplate-associated nicotinic a cetylcholine receptors (nAChR) in various rat skeletal muscles. We found a 20% increase in endplate-specific [I-125]alpha-bungarotoxin binding in seve ral muscles of trained rats, accompanied by equal susceptibility of toxin b inding to the inhibitory effect of D-tubocurarine in sedentary and trained muscles. We conclude that the neuromuscular junction adaptations that occur with increased chronic activation include an increase in nAChR number. Res ults of experiments designed to determine nAChR turnover also suggest that this effect is mediated by an alteration in the receptor's metabolic state. The potential implications and mechanisms of this adaptation are discussed . NeuroReport 9: 3549-3552 (C) 1998 Lippincott Williams & Wilkins.