Tomonori Kenmoku1, Noriko Nemoto2, Nahoko Iwakura3, Nobuyasu Ochiai4, Kentaro Uchida1, Takashi Saisu5, Seiji Ohtori4, Koichi Nakagawa6, Takahisa Sasho4, Masashi Takaso1. 1. Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0570, Japan. 2. Department of Bioimaging Center, Kitasato University School of Medicine, Sagamihara, Japan. 3. Department of Orthopedic Surgery, Tokyo Women's Medical University School of Medicine, Shinjuku, Japan. 4. Department of Orthopedic Surgery, Chiba University Graduate School of Medicine, Chiba, Japan. 5. Department of Orthopedic Surgery, Chiba Children's Hospital, Chiba, Japan. 6. Department of Orthopedic Surgery, Toho University Sakura Medical Center, Sakura, Japan.
Abstract
INTRODUCTION: This study assesses the effect of radial extracorporeal shock wave (rESW) exposure on neuromuscular transmission and neuromuscular junction (NMJ) morphology. METHODS: We applied 2,000 rESWs at 0.18 mJ/mm2 and a frequency of 15 Hz to the right calf of male rats, measured the compound muscle action potential (CMAP), and examined NMJ morphology using electron microscopy. Left calf muscles were used as controls. RESULTS: rESW exposure significantly reduced CMAP amplitude without delayed latency in exposed muscles compared with controls. All rESW-exposed muscles exhibited NMJs with irregular end plates. Mean interjunctional fold interval was significantly increased compared with controls. However, axon terminals and muscle fibers surrounding NMJs with irregular end plates were unchanged. DISCUSSION: This localized destruction of end plates may be caused by differences in acoustic impedance induced by the density of acetylcholine receptors. These results provide a possible mechanism for the effectiveness of rESW treatment for spasticity and dystonia. Muscle Nerve 57: 466-472, 2018.
INTRODUCTION: This study assesses the effect of radial extracorporeal shock wave (rESW) exposure on neuromuscular transmission and neuromuscular junction (NMJ) morphology. METHODS: We applied 2,000 rESWs at 0.18 mJ/mm2 and a frequency of 15 Hz to the right calf of male rats, measured the compound muscle action potential (CMAP), and examined NMJ morphology using electron microscopy. Left calf muscles were used as controls. RESULTS: rESW exposure significantly reduced CMAP amplitude without delayed latency in exposed muscles compared with controls. All rESW-exposed muscles exhibited NMJs with irregular end plates. Mean interjunctional fold interval was significantly increased compared with controls. However, axon terminals and muscle fibers surrounding NMJs with irregular end plates were unchanged. DISCUSSION: This localized destruction of end plates may be caused by differences in acoustic impedance induced by the density of acetylcholine receptors. These results provide a possible mechanism for the effectiveness of rESW treatment for spasticity and dystonia. Muscle Nerve 57: 466-472, 2018.