INFLAMMATION-INDUCED FOS PROTEIN EXPRESSION IN THE RAT SPINAL-CORD ISENHANCED FOLLOWING DORSOLATERAL OR VENTROLATERAL FUNICULUS LESIONS

Previous studies have shown an enhanced expression of Fos protein-like immunoreactivity in the lumbar spinal cord of rats viith complete spi nal transection following persistent hindpaw inflammation. To further locate the spinal pathways responsible for these effects, we compared the inflammation-evoked Fos expression in rats with bilateral lesions of the dorsolateral (DLFX) or ventrolateral (VLFX) funiculus, and with rats with a sham operation. The results indicate that the number of F os-labeled neurons was significantly increased in all laminae of the d orsal horn ipsilateral to the inflamed hindpaw and in contralateral de ep dorsal horn in both DLFX and VLFX rats compared to sham-operated ra ts. Moreover, when comparing DLFX and VLFX rats, in the ipsilateral sp inal cord, DLFX resulted in more Fos expression in the deep dorsal hor n; in contrast, a larger number of Fos-labeled cells in superficial la minae was observed in VLFX rats. These results suggest that modulatory systems, which descend in both DLF and VLF pathways, mediate the enha nced net descending nociceptive inhibition after persistent inflammati on, although the supraspinal sites of origin of each pathway are likel y functionally diverse. (C) 1998 Elsevier Science B.V.