ADRENAL-MEDULLARY GRAFTS SUPPRESS C-FOS INDUCTION IN SPINAL NEURONS OF ARTHRITIC RATS

Expression of immediate-early genes such as c-fos is thought to reflec t patterns of neuronal activity in the central nervous system. Prolong ed increases in Fos-protein-like-immunoreactivity (FOS-LI) are seen in the dorsal horn of adjuvant arthritic rats, and parallel increased pa in behavior. Grafts of adrenal medullary, but not control tissue, into the spinal subarachnoid space reduce pain behavior and suppress the i nduction of spinal Fos-LI in arthritic rats. This reduction is particu larly marked in superficial laminae (I-II), but is also significant in deeper laminae (III-IV and V-VI). The results of this study suggest t hat adrenal medullary transplants reduce spinal cord hyperactivation c onsequent to painful peripheral inflammation.