Relationship between changes in muscle fibers and CMAP in skeletal muscle with different stages of aging.

ABSTRACT

AIM: This study aimed to investigate the relationship between the changes of muscle fibers and the changesof peripheral nerve functions (CMAP) with aging. METHODS: Lewis rats enrolled in this study. Muscle biopsy and CMAP of tibialis anterior (TA) were measured. RESULTS: CMAP amplitudes increased significantly in 6 months (P<0.05). CMAP latencies of peroneal nerves found to be significantly higher in older rats (P<0.05). In 6 months these two muscle fibers went through a significant decrease (P<0.05). Type IIb and type IIx muscle fibers increased significantly in 6 months when compared with those in 1 month (P<0.05). After 6 months, the percentages of type I and type IIa muscle fibers increased as the month increased (P<0.05). The percentages of type IIb muscle fibers and type IIx muscle fibers dropped significantly as the month increased (P<0.05). Type I and type IIa muscle fibers were negatively related to CMAP amplitudes (P<0.05). Type IIb muscle fibers were positively related to CMAP amplitudes (P<0.05). CONCLUSION AND DISCUSSION: There is a shift from the fast types (Type IIx and IIb) to slow types (Type I and IIa) in muscle fibers with agingwhich is consistent with changes in CMAP amplitude of peripheral nerves.