Analgesic effects of intrathecal injection of dexmedetomidine in chronic constriction injury rat models

Objective To observe the analgesic effect of intrathecal dexmedetomidine in CCI induced rat models.Methods Thirty-six SD male rats were randomly divided into three groups(n=12): sham-operated group (group S); operation-control group (group C) and dexmedetomidine group (group D).The thermal withdrawal latency(TWL) and mechanical withdrawal threshold (MWT) were measured respectively using BME-410A plantar thermalgia tester and 37400-002 plantar haphalgesia tester. The rats were killed at the day 5 after intrathecal injection of dexmedetomidine and the L4-L5 lumbar segment of the spinal cord was removed for determination of the number of FLI-N(C-fos immunoreactive neurons) in dorsal horn with immunohistochemistry.Results The TWL and MWT in the groups C and D before intrathecal injection were lower than those of the group S(P0.05); The TWL and MWT in the group D after intrathecal injection were higher than the group C(P0.05); The number of FLI-N in the spinal cord dorsal horn was more in the group C than the group S(P0.05), but in the group D was less than the group C(P0.05).Conclusion Intrathecal injection of dexmedetomidine can attenuate the hyperalgesia induced by CCI which may be associated with the inhibition of the c-fos expression in spinal cord dorsal horn.