Identification of the Ca2+‐sensing receptor in rat trigeminal ganglia, sensory axons and tooth dental pulp

Studies suggest that extracellular Ca 2+ concentration regulate dentin formation. We have previously reported that sensory denervation reduces dentin formation. The Ca 2+ ‐sensing receptor (CaSR) is expressed in perivascular sensory nerves in mesenteric arterioles and in dorsal root ganglion. Our study was aimed to (1) identify CaSR in dental pulp (DP), sensory axons and trigeminal ganglion (TG) and (2) to investigate whether increased extracellular Ca 2+ increases tooth blood flow. Pulpal blood flow (PBF) was measured by laser‐Doppler flowmeter. The distribution of CaSR in jaws, DP and TG was studied by immunohistochemistry. RT‐PCR and Western blot were used to assess CaSR expression. Abundant expression of the CaSR was found in sensory axons and cells in the jaws, TG and DP. Activation by 5 mM Ca 2+ and NPS R‐467 resulted in increased PBF, suggesting that extracellular Ca 2+ regulates tooth blood flow. Iberiotoxin inhibited relaxation caused by extracellular Ca 2+ . RT‐PCR showed the presence of the CaSR message in TG and DP. Western blot analysis indicates expression of glycosylated and nonglycosylated forms of the receptor in TG and DP. It is concluded that the CaSR is present in the DP, sensory nerves and TG, and that increase in extracellular Ca 2+ concentration in the DP causes vasodilatation, which may provide a mechanism to regulate dentin mineralization. This work was supported by the Western Norway Regional Health Authority Fund and the Norwegian Research Council Project # 101330