Treadmill running upregulates the expression of acetylcholine receptor in rat gastrocnemius following botulinum toxin A injection.

Treadmill running is a commonly used training method for patients with spasticity to improve functional performance. Botulinum toxin has been widely used therapeutically to reduce contraction force of spastic muscle. However, the effects of treadmill running in neuromuscular junction expression and motor unit physiology on muscle following botulinum toxin injection are not well established. To assess the effects of treadmill running on neuromuscular recovery of gastrocnemius following botulinum toxin A (BoNT-A) injection, we observed changes in gene expression. We hypothesized that the expression of acetylcholine receptor (AChR), myogenesis, and nerve plasticity could be enhanced. Twenty-four Sprague-Dawley rats received botulinum toxin injection in right gastrocnemius and were then randomly assigned into untrained control and treadmill running groups. The rats assigned to the treadmill running group were trained on a treadmill 3 times/week with a running speed of 15 m/min for 8 weeks. The duration of training was 20 min per session. Muscle strength and gene expression of AChR subunit (α, β, δ, γ, and ε), MyoD, Myf-5, MRF4, myogenin, p21, IGF-1, GAP43, were analyzed. Treadmill running had no influence on gastrocnemius mass, but improved the maximal contraction force of the gastrocnemius in the treadmill running group (p < 0.05). Upregulation of GAP-43, IGF-1, Myo-D, Myf-5, myogenin, and AChR subunits α and β were found following treadmill running. The expression of genes associated with neurite and AChR regeneration following treadmill exercise was upregulated, which may have contributed to enhanced recovery of gastrocnemius strength.