Differential expression of neuropeptide Y Y1 receptors during pulpal inflammation

Abstract

To study the pattern of neuropeptide Y (NPY) Y1 receptor (Y1R) localization in the normal dental pulp and during different stages of pulpal inflammation. The hypothesis was that the expression of Y1R varies during different stages of pulpitis. Pulp exposure injury was made on first molar teeth of Sprague-Dawley rats. Animals were killed 3, 7, 14, 21, 28 and 46 days after pulp exposure. Jaws were removed, decalcified and processed for immunohistochemistry for identification and localization of Y1R. Double labelling was performed using antibodies for laminin, CD43 and CD4 with Y1R. RT-PCR was performed to verify gene expression of Y1R in dental pulp and trigeminal ganglion. RT-PCR revealed the presence of NPY-Y1R in the dental pulp, trigeminal ganglion and gingiva. With immunohistochemistry, in control rats, Y1R was mainly located in capillaries and small vessels in the dental pulp as well as in the odontoblastic layer. No YIR was noted on immune cells in normal pulp. In pulpitis, immune cells such as CD43+ granulocytes and CD4+ lymphocytes expressed Y1R. As pulpitis progressed, there was a significant decrease in number of blood vessels expressing Y1R in the odontoblast layer when compared to control rat pulp. This study gives evidence that Y1R is a modulator of pulpal inflammation.