Numerous adrenal chromaffin cell preparations fail to produce analgesic effects in the formalin test or in tests of acute pain even with nicotine stimulation

Previous studies have reported that intrathecal implants of a variety of ad renal chromaffin cell preparations all produce analgesic effects in rodents . The major objective of the present study was to determine if any adrenal chromaffin cell preparations produce more robust analgesic effects than oth er cell preparations. The present study included adult rat adrenal chromaff in tissue allografts, purified adult bovine chromaffin cells, and polymer-e ncapsulated calf adrenal chromaffin cells, all prepared according to previo usly published procedures, as well as purified calf adrenal chromaffin cell s. Previous studies have also suggested that immunosuppression may play a r ole in graft survival, and potentially increase the magnitude of analgesic effects, so the present study included both immunosuppressed and non-immuno suppressed groups (cyclosporin A, 10 mg/kg per day). Behavioral tests inclu ded the formalin test; and a dorsal tail-flick, hot-plate, and paw-pinch te st, conducted sequentially 2 min after systemic nicotine (0.1 mg/kg) to evo ke release from the chromaffin cells, as previously reported. Analgesic eff ects related to morphine and nicotine were detected, and consistent differe nces in performance could be detected between individual animals. surprisin gly, no analgesic effects were detectable with any of the four chromaffin c ell preparations, with or without immunosuppression, in the formalin test o r with nicotine stimulation in tests of acute pain. (C) 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All r ights reserved.