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[Decreased neurotrophin-3 expression of intrafusal muscle fibers in rat soleus muscles under simulated weightlessness.] [Article in Chinese]

REN Jun-Chan, FAN Xiao-Li^*, SONG Xin-Ai, SHI Lei

Department of Physiology and Pathophysiology, Medical College of Xi’an Jiaotong University, Xi’an 710061, China； Department of Biotechnology, School of Life Sciences and Technology, Xidian University, Xi’an 710071, China

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.

Key words: weightlessness; soleus muscle; muscle spindles; neurotrophin-3

Received: 2010-03-29　　Accepted: 2010-11-23

Corresponding author: 樊小力　　E-mail: fanxl@mail.xjtu.edu.cn

Citing This Article：

REN Jun-Chan, FAN Xiao-Li, SONG Xin-Ai, SHI Lei. [Decreased neurotrophin-3 expression of intrafusal muscle fibers in rat soleus muscles under simulated weightlessness.] [Article in Chinese]. Acta Physiol Sin 2011; 63 (1): 75-80 (in Chinese with English abstract).