• Akira Onda, Yasuaki Murata, Björn Rydevik, Karin Larsson, Shinichi Kikuchi, and Kjell Olmarker.
• Department of Orthopaedics, Sahlgrenska University Hospital, Göteborg University, Gothenburg, Sweden.
• Spine. 2005 Jan 15;30(2):188-93.

Study DesignThe time courses of nerve growth factor content and pain-related behavior were examined using experimental disc herniation models.ObjectivesTo investigate a relationship between nerve growth factor level and pain behavior.Summary Of Background DataAn induction of nerve growth factor in the periphery is regarded as a major contributor of inflammatory hyperalgesia and neuropathic pain. However, it has not been clarified quantitatively whether disc herniation induces changes in nerve growth factor levels in the dorsal root ganglion in relation to pain-related behavior.MethodsA total of 140 rats were used in this study. The animals had their left L4 nerve roots and associated dorsal root ganglion exposed and were equally divided into 4 groups: L4-L5 disc puncture, displacement of L4 nerve roots/dorsal root ganglion, the combination of disc puncture and displacement, and sham exposure. The content of nerve growth factor in the affected dorsal root ganglion was assessed by enzyme-linked immunosorbent assay as well as pain behavior during a postoperative 21-day period.ResultsDisc puncture resulted in nerve growth factor induction at postoperative day 3, but not apparent behavioral changes. Mechanical displacement induced nerve growth factor at postoperative day 1 and mechanical allodynia at postoperative day 3, respectively (P < 0.05). In the combination model, there were more pronounced changes in nerve growth factor induction and both mechanical and thermal threshold during 7 days after surgery (P < 0.05).ConclusionsThese data suggest the possibilities that elevated nerve growth factor level is partly involved in pain behavior and further the combined model mimicking the clinical situation, which causes the marked neuronal responses, is helpful to advance the understanding of the mechanisms underlying sciatica due to lumbar disc herniation.

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