Abstract: Objective: To study the expression of P2X receptors in the trigeminal spinal subnucleus caudalis (Vc) and the ventral posteromedial nucleus (VPM) induced by dental pulp inflammation.Methods: Cavities were prepared on the left first upper molars via a 1/2 # round ball drill, and the cavities with exposed dental pulp were left open to the oral microflora for 1, 3, 7 and 28 days. 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 from 1d to 7d, and chronic inflammation around the apical area of the root was observed after 28d. The P2X1-6 receptors were expressed in neurons, whereas P2X7 was expressed in microglia. Varying increases in the expression of the P2X1-7 receptors were characterized during acute and chronic pulp inflammation. The expressions of P2X2, P2X4 and P2X7 in the ipsilateral Vc, and P2X1-5 and P2X7 in the bilateral VPM, especially on the contralateral side were increased during acute inflammation process.Conclusion: The present findings suggest that all of the P2X receptors except P2X6 are involved in different ways in the Vc and VPM after dental pulp injury.

Key words: P2X, Dental pulp inflammation, Trigeminal ganglion, Trigeminal spinal subnucleus caudalis