Effect of Neuromuscular Electrical Stimulation of Denervated Muscle on the mRNA Expression of IGFs in Rat Skeletal Muscle and Sciatic Nerve

Abstract

[Purpose] In rehabilitation, it is important to prevent regressive change caused by denervated muscle atrophy. We determined the effect of neuromuscular electrical stimulation on expression of insulin-like growth factor-1 and 2, and their receptors' mRNA in skeletal denervated muscles and sciatic nerves of Wistar rats. [Methods] Denervation was performed by crushing the bilateral sciatic nerves. The day following the denervation, the bilateral gastrocnemius muscles were electrically stimulated percutaneously, for 30 min/day at 4 mA intensity and 10 Hz frequency. After 3 weeks, the muscles and crushed site of the sciatic nerve were dissected. [Results] Relative muscle weights were decreased by denervation; however, the decrease was less after electrical stimulation. Expression of insulin-like growth factor-1 and 2 mRNA in denervated muscle and sciatic nerve were increased by electrical stimulation. [Conclusion] In general, skeletal muscle growth and atrophy is regulated by insulin-like growth factor-1. The neurotrophic factors, including insulin-like growth factor-2, are produced in denervated muscle and initiate regeneration, and are transported retrogradely by axoplasmic transport. Therefore, our results demonstrate that electrical stimulation retards muscle atrophy and promotes nerve regeneration following denervation by increasing insulin-like growth factors' mRNA in the denervated muscle.