The effect of time interval between electrical stimulation on the denervated rat muscle O efeito do intervalo da estimulação elétrica no músculo desnervado de rato

Abstract Objective: To compare the effect of electrical stimulation (ES) applied daily and on alternate days, on the area density of the connective tissue (CT) and on the cross-sectional area (CSA) of the denervated muscle fi bers. Methods: Thirty-fi ve rats were divided into the following groups: control (C), denervated (D), denervated + daily electrical stimulation (D+DES) and denervated + alternate-day electrical stimulation (D+ES). The application of ES on the gastrocnemius was started 24 hours after nerve damage of axonotmesis type and was applied for 20 and 30 days. Cross-sections were stained with hematoxylin-eosin to measure the CSA and area density of CT. The statistical analysis consisted of the Shapiro Wilk test followed by analysis of variance (ANOVA) F (one-way) and the Tukey test (p≤ 0.05). Results: Analysis of the area density of CT showed that only the D+DES Group presented values similar to those of the C Group, for the two periods analyzed. There was no difference in CSA in the 20-day Group between the ES Groups and the D Group (p> 0.05). After 30 days, all the experimental groups reached CSA values similar to the C Group. Conclusions: The ES was ineffi cient for minimizing the muscle fi ber atrophy. However, the CT was responsive to ES, and daily applications were more benefi cial for the muscle than were alternate-day applications, thus suggesting that the interval for applying ES to denervated muscle is an important variable for CT adaptation.Key words: denervation; gastrocnemius; connective tissue; hypertrophy; electrical stimulation.