Muscle and nerve responses after different intervals of electrical stimulation sessions on denervated rat muscle

Electrical stimulation is a procedure used to treat denervated muscles. The number of electrical stimulation sessions varies across muscle rehabilitation protocols, from daily to certain days throughout the week. The purpose of this study was to evaluate how muscle and nerve respond to different intervals of electrical stimulation applied to denervated muscle. Denervation of rat gastrocnemius muscle was imposed via nerve crush, and electrical stimulation was applied to the muscle either daily (Monday through Friday) or on alternate days (Monday, Wednesday, and Friday). Four experimental groups were studied: denervated, denervated plus daily electrical stimulation, denervated plus alternate-day electrical stimulation, and control. On the 12th day after nerve crush, levels of MyoD, myostatin, and atrogin-1 gene expression, as well as muscle fiber and nerve morphometry, were evaluated. Expression levels of all three genes were higher in the denervated group when compared with control. Also, expression levels of MyoD and myostatin were higher in denervated plus alternate-day electrical stimulation and denervated plus daily electrical stimulation groups when compared with denervated. The denervated plus daily electrical stimulation group had lower atrogin-1 expression, lower density of intramuscular connective tissue, and better morphometric nerve characteristics when compared with the denervated and denervated plus alternate-day electrical stimulation. These results indicate that the responses of both muscle and nerve to electrical stimulation after muscle denervation depend on the intervals of electrical stimulation application.