Effects of electrical stimulation on neuromuscular junction morphology in the aging rat tongue

TLDR

Age‑related changes in cranial muscle neuromuscular junctions may impair swallowing, and while neuromuscular electrical stimulation is used therapeutically, its impact on NMJ structure and the optimal dimensionality for measurement remain unclear. The study compared two‑ and three‑dimensional NMJ morphology measurements in the genioglossus muscle of rats after eight weeks of hypoglossal nerve stimulation versus untreated controls. In old rats, the correlation between motor endplate and nerve terminal volumes was positive in only half of controls but in 89% of NMES‑treated rats, and three‑dimensional measurements proved more accurate, indicating that aging and NMES alter pre‑ and post‑synaptic relationships. Muscle Nerve 43: 203–211, 2011.

Abstract

Abstract Alterations in neuromuscular junction (NMJ) structure in cranial muscles may contribute to age‐related deficits in critical sensorimotor actions such as swallowing. Neuromuscular electrical stimulation (NMES) is used in swallowing therapy, but it is unclear how NMJ structure is affected or if NMJ morphology is best measured in two or three dimensions. Two‐ and three‐dimensional measurements of NMJ morphology in the genioglossus muscle were compared in rats that had undergone 8 weeks of hypoglossal nerve stimulation vs. untreated controls. The relationship between motor endplate volume and nerve terminal volume had a mean positive slope in 90% of the young adult controls, but it was positive in only 50% of the old controls; 89% of NMES old rats had a positive slope. NMJ measurements were more accurate when measured in three dimensions. In the NMJ, aging and NMES are associated with changes in the pre‐ and post‐synaptic relationship. Muscle Nerve 43: 203–211, 2011