Effects of exercise and muscle type on BDNF, NT-4/5, and TrKB expression in skeletal muscle.

Muscle-derived neurotrophins are thought to contribute to the adaptation of skeletal muscle to exercise, but the effects of brief exercise interventions on BDNF, NT-4/5, and trkB are not understood. RNA was extracted for RT-PCR from soleus and medial gastrocnemius of Sprague-Dawley rats exercised on a treadmill at speeds up to 20 m/min at 5% incline for 5 or 10 days. BDNF expression was elevated in soleus following 5 days (184%, P < 0.001) but not 10 days of exercise. NT-4/5 and trkB were not affected at either time-point. BDNF mRNA was significantly higher in soleus at rest when compared with medial gastrocnemius (193%, P < 0.05). No significant effects of muscle type were detected for NT-4/5 and trkB. Our results indicate differential control of BDNF expression between soleus and medial gastrocnemius following 5 days of exercise. BDNF may be a protein with an uncharacterized contribution to the acute adaptation of skeletal muscle to exercise, whereas NT-4/5 shows no response.