Characteristics of Muscle Fibers in Rats with Limb Movements during Sleep after Spinal Cord Injury

Abstract

Background/Aims: Previous studies have demonstrated that spinal cord injury (SCI) results in changes in sleep patterns through increased arousals and limb movements during sleep. Dramatic changes in muscle myosin heavy-chain isoforms have also been reported. The aim of this study was to investigate the characteristics of muscle fibers after SCI in rats with limb movements during sleep. Methods: Forty male Wistar rats were divided into four groups: SHAM, SCI 3, 7 and 15 days. Animals were subjected to electrode insertion surgery, 24-hour baseline sleep recording, SCI, and subsequent sleep recording for 3, 7, or 15 consecutive days. In addition, the gastrocnemius muscle and spinal cord were collected for histopathological/histochemical analyses. Results: Our results indicate a rapid and progressive decrease in the cross-sectional area of type I fibers in the gastrocnemius muscle (35.76–24.74 µm²) after SCI. Additionally, we found SCI-induced changes in sleep patterns. Following SCI, we also observed limb movements in sleeping rats, as well as significant negative moderate correlations between type I fibers and limb movement. Conclusion: Our study strengthened the hypothesis by correlation between changes in types of muscle fiber (decline in type I fibers) and an increase in limb movements during sleep after SCI.