| Part1Effects of LPS-induced dental pulp inflammation on the expression and role of P2X receptors in rat trigeminal ganglionAim:The ionotropic purinergic receptor family (P2X) is reported to mediate nociception in primary afferent neurons. This study aims to investigate the involvement of P2X receptors in the sensitization of the trigeminal ganglion (TG), the expression of the nociceptive factors in the TG induced dental pulp inflammation and the effect of the P2X inhibitor on the nociceptive factors.Material and methods:Lipopolysaccharides (LPS) were unilaterally applied to the pulp of the upper molar of the rat to induce dental pulp inflammation. The expression of c-fos, a marker of neuronal activity, was observed, and the expression pattern of the P2X receptors in the V1-V2division of TG was inverstigated by immunohistochemical staining and western blot. The relationship of the markers of glutamatergic afferents, VGluT1, and GABAergic afferents, GAD67, between the P2X receptors was observed. The inhibitor of the P2X receptor, TNP-ATP was injected in the left whisker pad of the rats, and the expression of c-fos, VGluTl, GABA, and the phosphorylation of the p38and ERK1/2were inverstigated by Western blot.Results:The retrograde tracer showed that the upper left first molar was innervated by the V1-V2division of the TG, and increased expression of c-fos was induced by pulp inflammation in V1-V2division, indicating the activation of TG neurons. The expressions of P2X2, P2X3and P2X5were also increased in the V1-V2division of TG from Id to3d, and the expressions of P2X2, P2X3and P2X5were primarily in small-sized neurons. The VGluT1and GAD67were induced by LPS and co-expressed with the P2X2, P2X3and P2X5receptors in small-sized TG neurons by double-immunofluorescent staining. The expression of the c-fos, VGluT1and GAD67was increased and the phosphorylation of the p38and ERK1/2were induced during acute dental pulp inflammation. The increases of the expression of c-fos, VGluT1, GAB A, and the phosphorylation of the p38and ERK1/2were inhibited by the application of the P2X inhibitor, TNP-ATP. Conclusion:The present findings suggest that the P2X2, P2X3and P2X5receptors are upregulated as part of the sensitization produced by dental pulp inflammation. Inhibiting the P2X receptors in the TG will down regulated the increases of the expression of c-fos, VGluT1, GABA, and the phosphorylation of the p38and ERK1/2induced by dental pulp inflammation.Part2The expression of the P2X receptors in the central nervous system of the rats induced by the dental pulp inflammationAim:Artificial tooth pulp exposure leads to dental pulp injury and inflammation, inducing hyperalgesia in central nervous systems. The aim of the study was to inverstigate the expression of the P2X receptors in the trigeminal spinal subnucleus caudalis (Vc) and the ventral posteromedial nucleus (VPM) induced by the dental pulp inflammationMaterial and methods:Cavities were prepared on the left first upper molars via a1/2#round ball drill, and the cavities with exposed dental pulp were left open to the oral microflora for1,3,7or28days. The Vc and VPM were harvested at specific time intervals and underwent further immunofluorescent and immunohistochemical procedures to assess the expression patterns of P2X1-7.Results:Acute inflammation was induced by dental pulp exposure from1d to7d, and chronic inflammation around the apical area of the root was observed at28d. The P2X1-6receptors were expressed in neurons, whereas P2X7was expressed in microglia. Varying increases in the expression of the P2X1-7receptors were characterized during acute and chronic pulp inflammation. The expression of P2X2, P2X4and P2X7in the ipsilateral Vc, and P2X1-5and P2X7in the bilateral VPM, especially on the contralateral side, was increased during acute inflammation process.Conclusion:The present findings suggest that all of the P2X receptors except P2X6are involved in different ways in the Vc and VPM after dental pulp injury. |
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