c-Fos induction in spinal cord neurons after renal arterial or venous occlusion

Experiments were done in the anesthetized rat to identify the dorsal root g anglia (DRG) and the spinal cord segments that contain neurons activated by either renal venous occlusion (RVO) or by renal arterial occlusion (RAO). Fos induction, detected immunohistochemically in DRG and the spinal cord ne urons, was used as a marker for neuronal activation. RVO induced Fos immuno reactivity in neurons in the DRG of spinal segments T-8-L-2 on the side ips ilateral to that of occlusion. The largest number of Fos-labeled neurons wa s found in the T-11 DRG. In the spinal cord the largest number of Fos-label ed neurons was found in the ipsilateral dorsal horn of spinal segments T-11 -T-12, predominantly in a cluster near the dorsomedial edge of laminae I-II . A few additional Fos-labeled neurons were observed in laminae TV and V. A fter RAO Fos-labeled neurons were found in the ipsilateral DRG of spinal se gments similar to those observed to contain neurons after RVO. However, mos t of the Fos-labeled neurons were observed within the T-12-L-1 DRG. In the spinal cord Fos-labeled neurons were scattered throughout lamina I-II of th e ipsilateral dorsal horn of spinal segments T-8-L-2, although the largest number was observed at the TIE level. Additionally, a distinct cluster of F os-labeled neurons was observed predominantly in the region of the ipsilate ral intermediolateral cell column, although a few neurons were found scatte red throughout the nucleus intercalatus, central autonomic areas, and lamin ae TV and V of the cord bilaterally. No Fos labeling was observed in the co mplementary contralateral DRG or dorsal horns after either RVO or RAG. Tn a ddition, renal nerve transection prevented Fos labeling in the ipsilateral DRG and dorsal horns after RVO or RAG. Taken together, these data suggest t hat functionally different renal afferent fibers activate DRG neurons that may have distinct projections in the spinal cord.