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At present,the mechanism of orofacial pain still remain unclear,the central sensitization is becoming one hot and difficult area of neuroscience research.In the pain research,many dental pulp injury models with different advantages have been employed,of which the acute pulpitis model is an ideal pathological pain model,which is of great value for the research of dental pulp and orofacial pain.Object:Based on the dinical characteristics of acute pulpitis,a rat acute pulpitis model was induced by Lipopolysaccaride(LPS),the expression of c-fos and GFAP in related nudeus of brain stem was observed to explore the mechanism of central sensitization,after that,the abnormally expressed proteins in the trigeminal ganglion were screened with a proteomics method to find pain-related proteins.Materials and methods:male rats were divided into experiment and control group.The access to dental pulp of the left upper first molar was prepared and LPS was placed into cavity,at 6h,12h,24h,48h after operation,the teeth were extracted,immunohistochemistry and western blot method were used to analyze the expression of c-fos and GFAP in brain stem,and proteomics method was carried out to detect the differential expression of function proteins in trigeminal ganglion.Results:1.HE staining:showed that with the increased stimulating duration of LPS,the range of inflammation extended gradually,and the inflammation became more severe.From 12 to 24h,the typical pathological change of acute pulpitis appeared,the pulp tissue became congested along with apparent exudate, great amounts of neutrophilic granulocyte infiltrated to the area below the perforation of pulp chamber,local abscess formed,necrosis appeared in partial dental pulp tissue,and odontoblast became malalinemented.After 48h, this pathological change extended to periapical tissue in partial animals.2.After central sensitization induced by LPS,the c-fos positive neuron number in Vc increased significantly compared with control group,which is also time-dependent and reach the peak at 24h after operation.Though the c-fos positive neuron number in contralateral side of Vc was lower than that in ipsilateral side,the development trend was similar with ipsilateral side.The number of c-fos positive neuron in NTs also increased significantly till 6h after operation,and then decreased gradually,but was sill higher than control group.3.The change of GFAP expression in Vc appeared later than c-fos,from 24 to 48h the number of positive neuron increased,the astrocyte became larger and the process became thicker,the staining also became stronger,the distribution of GFAP positive neuron was similar with c-fos.No apparent change was found in the contralateral side.The astrocyte in trigeminal ganglion only showed weak staining at 48h after operation.4.Total 48 protein spots were founded,among which 21 were upregulated,27 were downregulated.Ten proteins were identified as thyroxine binding globulin,ERp29,neurofilament protein,peripherin,serum albumin precursor, peripheral myelin P0 protein,Cathepsin B,pyruvate dehydrogenase E1, replication protein A and actin.Conclusion:1.Acute pulpititiscould be induced by LPS plcaed in exposed dental pulp in rat, which is a suitable model for hyperalgesia research;2.In this acute pulpitis,model,with the development the inflammation,neuron and astrocyte in related nucleus were activated in succession during the process of central sensitization,both the neuron and astrocyte acted reciprocally leading to central sensitization.3.Ten proteins identified in this research included structural protein,chaperone proteins,biosynthesis related protein,and some enzymeswhich play a key role in the stress and energy metabolism,based on this diversity,we conclude that the destruction of cytoskeleton,the change of energy metabolism and abnormal signal transduction all together take part in formation of central sensitization induced by acute pul pitis;4.ERp29,neurofilament protein and peripheral myelin P0 protein might be the biological indicators for the duration,degree and prognosis of acute pulpitis and the important dues for mechanism of orofacial pain,which might also provide the references for the diagnosis and treatment of orofacial pain.
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