Role of ketamine on the nerve function and neuropathic pain in diabetic rats

Objective To investigate the role of ketamine on the nerve function and neuropathic pain in diabetic rats. Methods 24 female Wistar rats weighing 180-220 g were randomized into 3 groups (n=8):normal control group (group N),diabetic neuropathic pain group (group D) and ketamine group (group K). Diabetic neuropathic pain model was induced by intraperitoneal streptozocin 65 mg/kg in groups D and K,in which rats were housed with food and water ad libitum for 4 weeks. From the 5th week the rats in group K received ketamine 10 mg/kg intraperitoneally once a day for another 4 weeks. At the end of the 8th week,mechanical withdrawal threshold (WMT) and nerve conduction velocity (NCV) were measured. Myelin sheath of sciatic nerve and Nissl bodies in neurons were demonstrated with staining of solechrome cyanin and buffered methylene blue,respectively. The levels of superoxide dismutase (SOD) and malonaldehyde (MDA) in the spinal cord were assayed by ELISA. Results The Nissl bodies in the spinal cord and the DRG neurons were observed to have pyknosis,accompanied by collapse and karyolysis of Nissl body. The myelin sheath of the sciatic nerve was characterized by edema of different degrees,vacuole-like denaturation,structural derangement and local demyelination. The neuropathies in myelin sheath and Nissl body were markedly attenuated in group K. Compared with group N,the levels of WMT,NCV and SOD were lower and MDA level higher in groups D and K (P0.05),while the comparison between the latter two groups revealed that groups K had higher levels of WMT,NCV and SOD and the lower MDA level. Conclusion Ketamine protects nerve and relieves the painful symptoms of neuropathic pain in diabetic rats by its antioxidative effect.