Adrenal medullary tissue transplants in the rat spinal cord reduce pain sensitivity

Adrenal chromaffin cells contain and release several neuroactive substances which induce analgesia when injected directly into the spinal cord (e.g. opioid peptides and catecholamines). Furthermore, the release of these substances can be induced by nicotine. In order to determine whether adrenal medullary tissue transplanted to the spinal cord can produce alterations in pain sensitivity, pieces of dissected rat adrenal medulla were placed in the subarachnoid space of rat spinal cords. Stimulation by a low dose of nicotine induced potent analgesia in animals with adrenal medullary transplants, but not in animals with control transplants. Furthermore, this analgesia was reversed to pre-nicotine levels by the opiate antagonist naloxone. Thus adrenal medullary transplants in the spinal cord may provide a permanent and locally available source of opioid peptides for the relief of intractable pain.