Functional State of the Neuromotor Apparatus of the Gastrocnemius Muscle in Rat Under Microgravity: Effect of Spinal Cord Stimulation

The aim of this study was the evaluation of the functional state of the neuromotor apparatus of the gastrocnemius muscle in rat under conditions of gravitational unloading, as well as in conditions of gravitational unloading combined with magnetic stimulation of the spinal cord. The electrical potentials of gastrocnemius muscle of the rat evoked by the stimulation of the sciatic nerve were recorded after a week of exposure the animal in the experimental conditions. Parameters of motor response and H-reflex were evaluated. It was found that gravitational unloading caused an increase of the reflex excitability of the motor centers of gastrocnemius muscle of the rat and magnetic stimulation of the spinal cord combined with unloading increased the intensity of transformations. In addition, it was registered the changes of the functional state of the muscle under conditions of gravitational unloading combined with the stimulation of the spinal cord. The detected transformations were probably associated with the activation of adaptation processes in the new motor environment (simulation of the microgravity, restriction of peripheral afferentation including the support afferentation).