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Objective P2X3 receptor plays important role in the onset and persistence of pain, recent study have shown that P2X3 receptor also plays roles during individual development.So we want to figure out whether pain in neonatal rat affects the expression level of P2X3 receptor in primary sensory neurons during development, and explore the potential mechanisms invloved.Methods Rats of postnatal 3, 7, 14, 21, 28 d and adult rats all received CCI (chronic constriction injury) operation in the left sciatic nerve, the right nerve received sham operation.Pain threshold (TWL and PWT) was assayed by thermal radiation and von Frey filament before and 1, 3, 7, 14, 21, 28 days after operation.Expression of P2X3 receptor in DRG of every group was measured by immunohistochemical staining (IHC), and the expression level was semiquantified.All statistical calculations were performed usingthe SPSS statistical package (SPSS, Chicago, USA).Results (1) After operation, thermal hyperalgesia and mechanical allodynia appeared on the neonatal and adult rats, and the change pattern of pain threshold in neonatal and adult rats is similar.The TWL and PWT decreased obviously from 1 d, descended to the lowest at 14 d post-operation, then returned to the normal level after 28 d post-operation.(2) The expression of P2X3 receptor in adult rat DRG increased obviously from 1 day post-operation and lasted for 21 days, and returned to the normal level after 28 days; while the expression of P2X3 receptor in neonatal rats DRG dropped obviously in all groups.Conclusion P2X3 receptor plays an important role in the incidence and development of pain and nervous system.And the result suggests that pain stimulus might affect the development of neonatal nervous system.