Abstract: The changes of spontaneous discharges and the evoked discharges induced by succinylcholine chloride of isolated muscle spindle of soleus muscle in rats which were hindlimb immobilization for one week were observed in the experiment, while the effects of adenosine triphosphate (ATP) on the afferent discharges of hindlimb immobilization rats were observed. The electrophysiological activities of isolated muscle spindle in vitro were recorded by the air isolation method. And the effects of different concentrations of 1， 2 and 3 mg/kg Na2ATP on muscle spindles′ afferent activities were also observed. The results showed that the spontaneous discharges from single muscle spindle of soleus muscle in rats which were hindlimb immobilization for 7d ays decreased spontaneously than normal(P<0.05), while the evoked discharges induced by Sch were not significantly increased. Given 1 mg/kg of Na2ATP, both the spontaneous and evoked discharges showed no significant change. Given 2 and 3 mg/kg of Na2ATP, the spontaneous discharge increased significantly (P<0.05), and the evoked discharges increased significantly after given 3 mg/kg Na2ATP(P<0.05). The results suggested that Na2ATP could increase spontaneously and evoke discharges caused by Sch of isolated muscle spindle in hindlimb immobilization rats, which may produce the effect of fighting muscle atrophy. This study provides significant data for the study of muscle spindle physiology and the experimental study of weightlessness induced muscular atrophy in rats.

Key words: hindlimb immobilization, adenosine triphosphate, single muscle spindle, spontaneous discharge, rats