mRNA expression of interleukins, phospholipase A(2), and nitric oxide synthase in the nerve root and dorsal root ganglion induced by autologous nucleus pulposus in the rat

The purpose of this study was to examine whether mRNA of interleukin-1 beta , interleukin-6, phospholipase A(2), and nitric oxide synthase was expresse d in the nerve root and dorsal root ganglion of an animal model in which ex posure to the nucleus pulposus induced mechanical hyperalgesia, a pain-rela ted behavior. Autologous nucleus pulposus obtained from coccygeal discs was relocated on the L4 and L5 lumbar nerve roots after partial laminectomy. T he reflex response to noxious mechanical stimuli to the hindpaw was mea mea sured preoperatively and to 4 weeks postoperatively. With a reverse transcr iption-polymerase chain reaction technique, expression of interleukin-1 bet a, interleukin-6, phospholipase A(2), and inducible nitric oxide synthase g enes in the nerve root and dorsal root ganglion was observed at 1, 2, and 4 weeks postoperatively. Mechanical hyperalgesia was observed from 3 days to 2 weeks postoperatively. The expression of interleukin-1 beta, phospholipa se A(2), and inducible nitric oxide synthase mRNAs increased after only 1 w eek. This increase was related to mechanical hyperalgesia. Expression of in terleukin-6 was detected in the neural tissue over time. It is possible tha t interleukin-1 beta, phospholipase A(2) and inducible nitric oxide in the nerve root or dorsal root ganglion, or in both, produce sciatic pain in the early stage of herniation of the lumbar disc.