Chromaffin cell transplants for alleviation of chronic pain.

Treatment of intractable pain with parenteral, subarachnoid, or epidural narcotics is often unsatisfactory due to tolerance and other systemic complications that accompany increasing dosages of these drugs. Other disadvantages include the potential infections with implantable pumps and the inconvenience of repeated narcotic administration. During the past several years, studies at the author's laboratory indicated that transplantation of adrenal medullary tissue or isolated chromaffin cells into the spinal subarachnoid space can significantly reduce pain in several rodent models without resulting in development of tolerance. Adrenal medullary chromaffin cells were selected because they produce high levels of both opioid peptides and catecholamines, agents that independently, and possibly synergistically, reduce pain when injected locally into the spinal subarachnoid space. The adrenal medullary transplants survive for prolonged periods, and continue to produce high levels of both catecholamines and met-enkephalin. These transplants reduce pain in two rodent chronic pain models, an arthritis model and a peripheral neuropathy model, both of which closely resemble human chronic pain syndromes. The success of the animal studies has led to initiation of human clinical trials in patients with chronic cancer pain; results are promising.