Objective    To investigate the effect of ondansetron on the development of neuropathic pain in rats following chronic constriction injury (CCI) on sciatic nerve.     Methods    This research consisted of 3 parts. ①A single bolus of ondansetron was given intraperitoneally 2 h before nerve injury; ②A single bolus of ondansetron was given intraperitoneally on the 7th day after nerve injury; ③Continuous administration of ondansetron was given daily for 35 d; In each part

male SD rats were randomly divided into ondansetron group (0.5

2

8 mg/kg)

saline group and sham operated group. The paw withdrawal response to thermal stimulation was tested throughout the 35 d following nerve injury.      Results    Ondansetron administration before nerve injury had no effect on thermal pain threshold in rats of experimental neuropathic pain. ondansetron administration on the 7th day after nerve injury attenuated the descending of thermal pain threshold but did not alter its descending trend in subsequent time period. Daily administration of ondansetron for 35 d attenuated and further delayed the descending of thermal pain threshold significantly in a dose-dependent manner.      Conclusion    Continuous administration of ondansetron can prevent or at least delay the descending of thermal pain threshold of rats with experimental neuropathic pain after constriction injury.