American Society for Peripheral Nerve

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Dynamic Changes of Acetylcholine Receptors (AChR) and Creatine Kinase (CK) Activity in Complete Denervated Muscle and Protective Effect of Laser Phototherapy
Shimon Rochkind, MD1; Asher Shainberg, PhD2
1Division of Peripheral Nerve Reconstruction, Departments of Neurosurgery, Tel Aviv Sourasky Medical Center, Tel Aviv University, Tel Aviv, Israel; 2 Faculty of Life Science, Bar-Ilan University, Ramat Gan, Israel

Background: Post-traumatic prevention of muscle atrophy is a major challenge in restorative medicine. When muscles are denervated, as in cases of complete peripheral nerve injury, they deteriorate progressively. Denervated muscles can account for significant differences in the extent of AChR and CK activity during the denervation period. This study was designed to assess the status of skeletal muscles during long-term denervation processes, by investigating changes in the level of AChR and CK activity in the denervated gastrocnemius muscle of the rat. The influence of low power laser irradiation (laser phototherapy) on muscle degenerative process was also analyzed.

Methods: The study was conducted on 96 rats: 48 that received laser treatment and 48 untreated controls. The gastrocnemius muscle was denervated by removing a 10mm segment of the sciatic nerve. Low power laser irradiation was delivered transcutaneously to the right gastrocnemius muscle 30 min for 14 consecutive days. Under general anesthesia, the rats were euthanized at seven time points: 7, 14, 21, 30, 60, 120, and 210 days, with and without laser treatment respectively. AChR was quantified by the 125I-a-bungarotoxin. CK activity was measured by a specific spectrophotometric method.

Results: Muscle denervation results is progressive degradation of AChR and CK content. After 4 months for AChR and 2 months for CK content we found partial preservation in both components until 7 months after complete muscle denervation. Laser treatment had a significant therapeutic effect on the denervated muscle during the first 21 days for AChR and the first 30 days for CK activity.

Conclusions: We suggest that survival of denervated muscle is longer than previously considered. In the early stages of muscle atrophy, laser phototherapy may preserve the denervated muscle by maintaining CK activity and the amount of AChR close to its initial level before injury.

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