SITES OF RENAL PAIN PROCESSING IN THE RAT SPINAL-CORD - A C-FOS STUDYUSING A PERCUTANEOUS METHOD TO PERFORM URETERAL OBSTRUCTION

The sites of renal pain processing in the rat spinal cord were studied by mapping the spinal cord neurons expressing c-Sos after acute urete ral distension due to obstruction. A new experimental model is present ed. A nylon knot was loosely placed around the ureter and the ends of the thread exteriorized through the retroperitoneal wall. Eight days l ater, when all c-fos expression due to nociceptive input from the abdo minal wound and the manipulation of the intestines had disappeared, th e nylon ends were pulled to produce ureteral occlusion, C-fos activati on occurred at spinal segments T10-L4 with a peak at L1-L2. The activa ted neurons were concentrated in laminae I, lateral IV-V, medial VIT a nd X. While in lamina I nearly all Fos-immunoreactive cells were ipsil ateral, in the deeper laminae taken together 60% cells were ipsilatera l and 40% contralateral to the distended ureter. It is suggested that renal nociceptive input giving rise to conscious pain perception is tr ansmitted through ipsilateral lamina I, whereas input triggering auton omic reflexes may be mainly processed, ipsi-and contralaterally, in th e deep laminae. (C) 1997 Elsevier Science B.V.