title: [Decreased neurotrophin-3 expression of intrafusal muscle fibers in rat soleus muscles under simulated weightlessness].
abstract: The present study aimed to study the changes of neurotrophin-3 (NT-3) expression of intrafusal muscle fibers in rat soleus muscles under simulated weightlessness. The tail-suspension (SUS) rat model was used to simulate weightlessness. Forty mature female Sprague-Dawley rats were randomly assigned to ambulatory control (CON), 3-day SUS, 7-day SUS, 14-day SUS and 21-day SUS groups. Immunohistochemistry ABC staining method and enzyme linked immunosorbent assay (ELISA) were used to detect the NT-3 expression of intrafusal muscle fibers in rat soleus muscles. The results from the immunohistochemistry staining technique showed that the extrafusal muscle fibers did not exhibit the NT-3-like immunoreactivity, and NT-3-like immunoreactivity was mainly expressed in nuclear bag 1 and nuclear bag 2 fibers of the muscle spindles. The ELISA results showed that the expression quantity of NT-3 in rat soleus muscles in control, 3-day SUS, 7-day SUS, 14-day SUS and 21-day SUS groups were (14.23±1.65), (14.11±1.53), (13.09±1.47), (12.45±1.51) and (9.85±1.52) pg/mg of tissue respectively. Compared to the control group, the expression quantity of NT-3 was significantly decreased after 14 days of SUS (P<0.05). After 21 days of SUS, the NT-3 expression was further reduced (P<0.01). These results suggest that simulated weightlessness induces an obvious decrease in the NT-3 expression level of intrafusal fibers in rat soleus muscles. Accompanying the simulated weightlessness extension, NT-3 expression in rat soleus muscle spindles is progressively decreased. These changes may contribute to the proprioceptive adaptations to microgravity.
authors.affiliation: Department of Physiology and Pathophysiology, Medical College of Xi'an Jiaotong University, Xi'an 710061, China.
authors.forename: Jun-chan
authors.initials: JC
authors.lastname: Ren
authors.forename: Xiao-li
authors.initials: XL
authors.lastname: Fan
authors.forename: Xin-ai
authors.initials: XA
authors.lastname: Song
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
mesh_terms: D000818:Animals; D015536:Down-Regulation; D005260:Female; D019417:Hindlimb Suspension; D009470:Muscle Spindles / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D020933:Neurotrophin 3 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018474:Weightlessness Simulation
chemical_list: D020933:Neurotrophin 3; D012333:RNA, Messenger