P>Objective To establish an immortalized rat astrocyte strain (IAST) expressing enkephalin regulated by doxycycline (Dox) and observe its analysesic effect on rat chronic neuropathic pain. Methods Retrovirus infection method was employed to develop an immortalized rat astrocyte strain expression enkephalin regulated by doxycycline. hPPE gene expression level of IAST/TetOn/hPPE strain was detected by Real time PCR and radioimmunoas say. Its analgesic potential was investigated by mechanical paw withdrawal thresholds after these cells were implanted into the subarachnoid space of chronic constrictive injury (CCI) rats. The expression of Fos protein in the dorsal horn of spinal cord was determined by immunohistochemistry. Results An immortalized rat astrocyte strain secreting enkephalin under the control of doxycycline was established successfully. After transplantation of IAST/TetOn/hPPE cell into the subarachnoid space of chronic constrictive injury (CCI) rats, the sensitivity of mechanical allodynia and the expression of Fos protein were significantly decreased (P<005), so the transplantation of IAST/Tet On/hPPE cell alleviated significantly CCIinduced chronic neuropathic pain in rats and the analgesic effect was also able to be regulated by Dox.Conclusion An immortalized rat astrocyte strain expressing enkephalin regulated by Dox has been established, which may provide a new tool for regulatable