Apoptosis in young and old denervated rat skeletal muscle.

INTRODUCTION: We investigated the apoptotic response to different degrees of denervation in young and older rats randomized into control (C), partial (PD), and complete denervation (CD) of muscles innervated by the sciatic nerve.

METHODS: Muscle wet weight to body weight (MWW/BW), myosin heavy chain (MHC) isoforms, and fiber cross-sectional area were determined in gastrocnemius and soleus muscles. Apoptotic responses were determined by changes in myonuclei and expression of Bcl-2 and BAX.

RESULTS: PD and CD resulted in significant reductions in MWW/BW and FCSA in both young and older rats. Older controls had greater apoptotic responses than young controls. Apoptotic responses were greater in PD and CD than in C in both age groups. No statistical interaction between denervation and age group was seen.

CONCLUSIONS: Older age was associated with increased level of apoptosis, but older muscle was not more vulnerable to the effect of denervation. Muscle Nerve 55: 262-269, 2017.