Expression Of NGF Amd BDNF In The Dorsal Root Ganglion And The Spinal Dorsal Horn In The Rat Following Peripheral Inflammatory Hyperalgesia

Object : Recent breakthrought in our understanding of pain mechanisms can be traced to the introduction of molecular biology techniques into pain research. Nerve growth factor(NGF), the first target-derived trophic factor to be discovered, is selectively trophic for small fiber sensory neurons and sympathetic ganglion neurons. There is increasing evidence that NGF plays role in the hyperalgesia associated with inflammation . Brain derived neurotrophic factor play a critical role in the altered nociceptive processing in the presence of inflammation . In this study, We focus on the expression and relationship of NGF^ SP, BDNF and mRNA in the DRG and spinal cord following peripheral inflammation.Method : Experiment inflammation produced by anintraplantar injection of 5% formalin in right hindpaw of adult rats. We evaluated the expression of NGF in inflammatory skin, DRG and dorsal horn neuron as well as changes in expression of SP ,BDNF protein and mRNA in the DRG and dorsal horn neuron at 2h^ 24h and 48h following inflammation pain, by means of immunochemisty.in situ hybridization and image analysis method. Effects of neurotrophic factors on peripheral and central sensitization in course of inflammatory pain were discussed.Result : All rats in pain group manifested bi-phasicnociceptive response of formalin-induced. NGF started to increase 2h after injection in inflammatory skin , ipsilateral DRG and dorsal horn neurons, and reached the hightest level 24h after injection. Expression of SP in ipsilateral dorsal horn neuronsincreased obviously 2h after injection, while in DRG remained unchanged until 24h after injection . Expression of BDNF in ipsilateral DRG and dorsal horn neurons were unchanged 2h after injection , and started to increase 24h after injection . Positive corelationship between the expression of NGF in ipsilateral DRG and dorsal horn neurons, and between the expression of NGF and BDNF in ipsilteral DRG neurons were found .Conclusion: NGF, as an important transmitter in the peripheral machenism of inflammatory pain, increased markedly in inflammatory tissue in the early stage of peripheral inflammatory pain, and was transfered to DRG and surface of dorsal horn retrogradely . Expression of SP and BDNF in ipsilateral DRG and dorsal horn neurons increased 24h after injection , showing a positive corelation with expression of NGF, which contributed to central sensitization through facilitating expression of SP and BDNF in dorsal horn neuron.