2007 Volume 13 Issue 1 Pages 10-16
Recent advances in the basic study on the nerve tissues innervating the lumbar intervertebral disc were digested. Nociceptive fibers and receptors are found in the outer layer of the annulus fibrosus with histological, immunohistochemical, and electrophysiological methods, demonstrating that disc disorders cause acute pain. Sensory fibers projecting to the rat L5-L6 disc are mainly derived from the L2 dorsal root ganglion (DRG) for the ventral and lateral portions, whereas they are from L5 in the dorsal portion. The segmental levels of the innervating DRGs are 7 and 9 for the ventral and dorsal portions, respectively. This structure of innervation should be considered in planning of nerve block and surgery. Sympathetic sensory fibers are abundant in the dorsal portion of the disc, and they play a role as nociceptors in inflammatory conditions. Nerve growth factor (NGF) sensitive neurons are predominant in small-sized nociceptive DRG neurons. NGF sensitive fibers and neurons increase in experimental disc inflammation models.