[Neuromotor apparatus in the condition of gravitational unloading: central and peripheral effects]

The functioning of central and peripheral structures of the gastrocnemius m. neuromotor apparatus was studied in rats exposed to simulated gravitational unloading. Gastrocnemius reflex (H) and motor (M) responses evoked by electrical stimulation of the sciatic nerve were measured after 7, 14, 21 and 35 days of tail-suspension. It was shown that thresholds of registered potentials went down on all days of testing; the H-amplitude rose during every testing and M-amplitude rose after 35 days of the gravitational unloading. Results of the experiments indicate changes in the functioning of motor centers that modulate properties and characteristics of peripheral neuromotor structures. The observed rearrangements can be caused by reduction of the afferent inflow.