Abstract
INTRODUCTION: Neuromuscular electrical stimulation (NMES) for the treatment of swallowing disorders is delivered at a variety of stimulation frequencies. We examined the effects of stimulation frequency on tongue muscle plasticity in an aging rat model. METHODS: Eighty-six young, middle-aged, and old rats were assigned to either bilateral hypoglossal nerve stimulation at 10 or 100 Hz (5 days/week, 8 weeks), sham, or no-implantation conditions. Muscle contractile properties and myosin heavy chain (MyHC) composition were determined for hyoglossus (HG) and styloglossus (SG) muscles. RESULTS: Eight weeks of 100-Hz stimulation resulted in the greatest changes in muscle contractile function with significantly longer contraction and half-decay times, the greatest reduction in fatigue, and a transition toward slowly contracting, fatigue-resistant MyHC isoforms. DISCUSSION: NMES at 100-Hz induced considerable changes in contractile and phenotypic profiles of HG and SG muscles, suggesting higher frequency NMES may yield a greater therapeutic effect. Muscle Nerve, 2018.