Effect of spinal glutamate transporter 1 on chronic constriction injury of sciatic nerve and morphine tolerance of rats

In order to investigate the role of spinal glutamate transporter 1 (GLT-1) in the neuropathic   pain and morphine tolerance, rat chronic constriction injury (CCI) of sciatic nerve was performed, and the    mechanical allodynia was evaluated by mechanical withdrawal threshold (MWT), the expression of GLT-1 was measured by real-time PCR and Western blotting analysis.  The results showed that compared to sham group, the MWT of CCI group had decreased approximately 80%.  Administration of morphine alone could develop tolerance rapidly in initial two days, and then had no significant difference with CCI group, the expression of GLT-1 was down-regulated.  Ceftriaxone sodium alone could improve mechanical allodynia.  Co-administration of ceftriaxone sodium with morphine attenuated morphine tolerance and up-regulated GLT-1 expression, and the MWT remained at high level after 6 days.  In conclusion, change of spinal GLT-1 expression and function has close correlation with the development of neuropathic pain and morphine tolerance.