The morphological changes in muscle spindles and alterations in cell activity of the rats' red nucleus after 2 weeks' simulated weightlessness / 西安交通大学学报·英文版

ABSTRACT

Objective: To study the morphological changes of soleus muscle spindle and electrical activity of neurons in Red Nucleus(RN) of the rat after 2 weeks' simulated weightlessness, and to reveal the interaction between proprioceptive inputs of muscle spindles and reciprocal alterations in RN under simulated weightlessness. Methods: Twenty female rats were exposed to weightlessness simulated by tail-suspension for 14 days (SW-14d). Body weight(200 -220 g) matched female rats were control group (Con). The morphological changes in isolated muscle spindle of soleus muscle, the discharges of red nucleus neurons were observed after 14d tail-suspensions by silver staining and extracellular recording respectively. Results: Compared with control group, the nerve ending of muscle spindle in SW-14d was distorted, degenerated and dissolved; the diameters of intrafusal fibers and capsule in equatorial region of soleus muscle spindles were diminished(P<0.05). The spontaneous cell activity and discharge of RN neurons (spikes/ s) induced by afferent firing from muscle spindles after injection of succinylcholine were reduced after 2 weeks' simulated weightlessness respectively (18.44±5.96 vs. 10.19±6.88, 32.50±8.08 vs. 16.86±5.97, P<0.01). Conclusion: The degeneration of muscle spindle induced by simulated weightlessness may be one of the causes that led to alterations in discharges of RN.