['An electrophysiologic study to examine responses of dorsal horn neurons in the rat L5 spinal cord to noxious stimuli after disc herniation or application of the nucleus pulposus to the L5 nerve root.', 'To investigate the pathogenic role of nucleus pulposus in the neural mechanism underlying sciatica and low back pain.', 'Application of the nucleus pulposus to the lumbar nerve root induced morphologic, vascular, and functional changes in the nerve root, suggesting that some factors in the nucleus pulposus may be implicated in the pathogenesis of chronic changes. However, it has not been studied whether the epidural application of nucleus pulposus enhances nociresponses of pain-processing neurons in the superficial dorsal horn of the spinal cord.', 'Extracellular recordings were made from the L5 dorsal horn neurons in 20 Wistar rats. The wide-dynamic-range (WDR) neurons activated by electric stimulation of the ipsilateral footpad of hindpaw were selected, and their responses to noxious and innocuous stimulation were examined after L5-L6 disc herniation onto the L5 nerve root (Group A) and application of the autologous nucleus pulposus (Group B) or fat tissues (Groups C and D).', 'The herniation of the nucleus pulposus (Group A) and application of the autologous nucleus pulposus (Group B) to the nerve root remarkably enhanced responses of WDR neurons to noxious stimuli for hours, whereas application of fat tissue scarcely enhanced nociresponses (Groups C and D).'] Does epidural application of nucleus pulposus enhance nociresponses of rat dorsal horn neurons?