Abstract: Objective To investigate the changes in the afferent discharge activities of the sensory nerve endings in muscle
spindles of rats with hindlimb immobilization. Methods Plaster cast was used immobilize the hindllimbs of rats. Using air-gap
technique, the spontaneous discharge of the muscle spindles and its responses to perfusion with succinylcholine (0.05 mg/ml)
and suspension in an extended position were observed in isolated muscle spindles from rats with hindlimb immobilization for
3, 7, and 14 days. Results The muscle spindles of rat soleus showed a sharp decrease in spontaneous discharge frequency (P<
0.01) and response to succinylcholine perfusion after 3 days of hindlimb immobilization (P<0.05). Significant changes of the
firing rate in an extended position was observed in rats after a 14-day immobilization (P<0.01). The duration of individual
spikes was significantly prolonged following hindlimb immobilization (P<0.01). Conclusion Muscle spindle discharges
decrease significantly in rats following hindlimb immobilization, which might be related to reduced contractile properties of
the muscle spindle.