Neurotrophins improve neuromuscular transmission in rats with myasthenia gravis

Myasthenia gravis is a disease of the neuromuscular junction (NMJ) associated with autoimmune destruction of the motor end‐plate. Inhibitors of acetylcholine (ACh) esterase are commonly used to mitigate symptoms by increasing ACh availability at the NMJ. Brain‐derived neurotrophic factor (BDNF) improves neuromuscular transmission in the rat diaphragm muscle (DIAm) by maintaining ACh release with repeated activation. We hypothesized that BDNF will mitigate the deficit of neuromuscular transmission in a passive transfer model of myasthenia gravis. Female Lewis rats were injected with vehicle, McAb1 (that does not induce myasthenia), and a myasthenogenic McAb3 antibody. Neuromuscular transmission failure (NMTF) was determined in DIAm‐phrenic nerve preparations by comparing the isometric force evoked by phrenic nerve stimulation and that evoked by superimposed direct muscle stimulation. After 2 min of repetitive stimulation, neuromuscular transmission was significantly impaired in myasthenic animals (NMTF: 80%) compared to vehicle and McAb1 animals (NMTF: ~60%). Exogenous BDNF treatment significantly improved neuromuscular transmission in all groups and NMTF in McAb3‐treated rats was no longer different from control or McAb1‐treated animals. We conclude that BDNF improves neuromuscular transmission in adult myasthenic rats. Supported by a Career Development Award from Mayo Clinic.