Morphofunctional Evaluation of Rat Leg Muscles under the Influence of Hindlimb Unloading, Tenotomy, and Denervation

Skeletal muscle atrophy can develop under the influence of various factors related to their disuse, such as immobilization, denervation, or exposure to microgravity. The aim of this work was to conduct a morphological and functional assessment of skeletal muscles in disuse models in rats. The rats were randomly assigned to a control group and groups that underwent denervation, tenotomy, and hindlimb unloading. During the experiments, a decrease in the diameter of muscle fibers was revealed in all experimental groups. During tenotomy, there was a decrease in dystrophin immunosuppression. During hindlimb unloading, the dystrophin level decreased, but by day 35, recovery was observed in the gastrocnemius and anterior tibial muscles, while in the soleus it continued to fall. After denervation, the dystrophin content also decreased, but then increased, reaching control values for the soleus muscle by day 35. The level of neuronal NO-synthase significantly decreased in all experimental groups. The effects of denervation and tenotomy lead to pronounced changes in the contractile function of the soleus muscle in rats, which are in direct correlation with the development of atrophic processes.