Introduction: Motor neurons in spinal cord dictate the structural and contractile properties of muscles. Damage to motor neurons change muscles gene expression pattern. Given that Neurotrophin-4 (NT-4) is required for survival and normal function of muscle fibers, the aim of present study is investigation effect of Decreased activity model as Spinal Nerve Ligation on muscular NT-4 gene expression.
 
Materials & methods: Ten adult male wistar rats in the weight range of 250±20 gr randomly were divided into two groups including healthy control (C), Spinal nerve ligation (SNL). Over the six weeks after SNL, neuropathic pain behavior tests were conducted continually in groups. In the end of Sixth weeks, change of NT-4 gene expression in soleus muscle was measured with Real time technique.
 
Findings: Behavioral tests demonstrated that spinal nerve ligation induce thermal Hyperalgesia and mechanical Allodynia in the SNL group which decreased pain threshold seen in allover period of study (P≤0.05). Also, compared to the C group, NT-4 gene expression in soleus muscle was higher in SNL group significantly (P≤0.05).
 
Discussion & conclusions: The present study demonstrated that decreased activity in the form of SNL is associated with increased NT-4 gene expression in soleus muscle. However, the mechanisms and pathophysiologic issues of this increase are remaining elusive.