Objective To observe the neurotoxicity of epidural different dose of dexmedetomi-dine in combination with 0.75% bupivacaine.Methods Twenty-five rabbits weight 2-3 kg without gender tendency and equipped with an epidural lumbar catheter were allocated randomly to five groups with 5 cases each.The control group (group C)received injections of 1.5 ml normal saline,0.75%bupivacaine 1.5 ml plus normal saline 0.5 ml in group B,and the other treatment groups received in-jections of 0.75% bupivacaine 1 ml plus dexmedetomidine 0.1 μg/kg (group D1 ), 0.75%bupivacaine 1 ml plus dexmedetomidine 0.2 μg/kg (group D2 )or 0.75% bupivacaine 1 ml plus dexmedetomidine 0.4 μg/kg (group D3),in the same volume of 1.5 ml.After successive 3-day epi-dural administration of the drugs and a 3-day observation,the rabbits were killed and the spinal cord was examined under optical and electron microscope.Results Serious damages of neuron were found in 1 animal from group D2 and 2 from group D3 under optical microscope.There was unclear bounda-ries between gray and white matter.Some nerve cells appeared necrosis in the grey matter of spinal cord and the number of nerve cells was decreased.Some reversible changes were found in all groups under electron microscope.Conclusion Epidural administration of dexmedetomidine can induce spinal cord and spinal nerves injury dose-dependently,and the motor function can recuperated completely.