ObjectiveTo study wether muscle spindle afferents have the regulating effects on res piratory movement. MethodsExperiments were performed on 36 anesthetized, immobilized, bilater ally vagotomized and artificially ventilated rabbits. Using the phrenic nerve discharge as the respira tory index, this experiment have assessed the effects of muscle spindle afferents invoked by intraarte rial injection of succinylcholine(Sch) on respiration. Results①In 40(63.49% ) cases which had the facilitated effects, 23 (36.51%) cases had the effect of prolonged inspiratory phase and 17 (26.98 % ) cases had the effect of attenuated expiratory phase and augmented respiratory frequency. In addition,there were 11(17.46% ) cases which had the attenuated effects,and 4(6.35% ) cases which had the biphasic effects,and 8(12.7% ) cases which had no effects;②The effect of prolonged inspiratory phase mainly showed the prolongation of inspiratory duration(Ti), but the effect of at tenuated expiratory phase and augmented respiratory frequency mainly showed the decrease of expi ratory duration (Te) and the augmentation of respiratory frequency(RF) ;③The above facilitated ef fects of Sch were significantly attenuated by intramuscular application of bupivacaine to destroy the muscle spindles. ConclusionThese results suggest that muscle spindle afferents induced by intraar terial injection Sch have a significant facilitated effect on respiration.

Objective To study counteracting effects of high frequency vibration on simulated weightlessness-induced atrophy of soleus muscles in rats. Methods Female Sprague-Dawley (SD) rats were assigned randomly to one of the three groups: simultaneous control (CON), simulated weightlessness (SUS), and SUS plus high frequency vibration (SUS+HFV). Soleus muscles were examined 7 days later. Sections were treated with adenosinetriphosphatase (ATPase) stain. The cross-sectional areas (CSA) of fibers, the relative proportion of types I and II were measured using Leica image analysis system. Results Compared with those of CON, the wet weight /body of soleus and the cross-sectional areas (CSA) of type I/II fibers in SUS were significantly reduced. The relative proportion of type I fibers in SUS was reduced and type II fibers increased. In SUS+HFV group, the wet weight/body of soleus and the cross-sectional areas (CSA) of type I/II fibers recovered completely. The relative proportion of type I/II fibers recovered completely. Conclusion The present study demonstrates that HFV is effective in counteracting the muscle atrophy induced by simulated weightlessness.

Objective To observe the effect of inosine on afferent discharge of muscle spindle.Methods The afferent discharge of isolated toad muscle spindle was recorded using air-gap technique.The effects of inosine on the discharge rate of muscle spindle was observed.Results After administration of 0.2mmol/L,0.4mmol/L and 0.8mmol/L inosine,the spontaneous discharge of muscle spindle increased from(0.86?(0.12))Hz,(0.88?(0.12))Hz and(0.85?0.10)Hz to(11.42?2.48)Hz,(21.75?3.03)Hz and(32.25?4.08)Hz,respectively.Conclusion Inosine can increase the afferent discharge rate of muscle spindle,and this effect is dose-dependent.