BACKGROUND: Despite of numerous researches on the mechanisms and new therapeutic methods of chronic pain, patients are still suffering even with the help of opioids. In recent years, however, with the development of molecular-biology cell transplantation gives us a new chance for treating intractable chronic pain. The major purpose of the present study was to determine if the chromaffin cells have robust analgesic effects in the spinal atlanto-occipital subarachnoid space even without nicotine stimulation. METHODS: In order to determine whether cultured bovine adrenal medullary chromaffin cells transplanted in the spinal cord can produce analgesic effects, we purified adrenal medullary chromaffin cells and implanted them into the subarachnoid space of rats' (n = 10) spinal cord without immunosuppression, and investigated the hot sensitivity of rats' hind-paw by a light-beam test. RESULTS: It was found that compared with the control group, hot response latency of the group which received adrenal medullary chromaffin cells had increased at 14 days and the analgesic efficacy was maintained for at least 3 months. CONCLUSIONS: Adrenal medullary chromaffin cells transplanted in the rats' spinal cord may provide a permanent and locally available source of neuropeptides for the relief of intractable pain. Furthermore, these kinds of analgesic effect even produced without any stimulation such as nicotine.