Subarachnoid spinal cord transplantation of adrenal medulla suppresses chronic neuropathic pain behavior in rats

Several weeks after transection of the sciatic and saphenous nerves, rats respond by self-injury of the denervated limb ('autotomy'). This behavior serves as a model of neuropathic pain. In this study we allografted fragments of rat adrenal medulla into the subarachnoid space of other rats, at lumbar spinal cord level, in an attempt to suppress autotomy behavior. The results show that autonomy was reduced by an average of 63% throughout the 8 week observation period. Catecholamine (CA) histofluorescent staining performed up to 120 days postoperatively (PO) revealed viable transplants in 75% of the rats. Transplant viability correlated with suppression of autotomy. This suggests that medullary chromaffin cells function as a local, long-lasting source of anti-nociceptive agents at the spinal segments which process input from the injured nerves.