Expression And Distribution Of Metabotropic Glutamate Receptor MGluR5 In Human Normal And Inflammatory Dental Pulp

Objective:mGluR5 mediates modulatory responses by coupling to guanine nucleotide-binding proteins. Besides its action in the brain, glutamate plays a key role in excitatory neurotransmission in the mammalian spinal cord and may be involved in pathological conditions of the spinal cord via excitotoxicity. It has previously been shown to play a role in pain transmission during inflammatory or neuropathic pain states. mGluR5 receptor is activated to enhance pain states, so selective mGluR5 antagonist,2-methyl-6-(phenylethynyl)pyridine (MPEP)is used to ease pain. The tooth pulp has a dense sensory innervation which, upon stimulation, conveys sensory signals perceived as pain. This innervation originates from the trigeminal ganglion. For the past few years, an experiment shows mGluR5 is expressed in human normal coronal pulp, however no define datas show mGluR5 is exsited in human inflammatory pulp or normal pulp else. This experiment checks the expression and distribution mGluR5 in human inflammatory pulp or normal pulp else by immunohistochemistry. We observe and explore the change and the role states of mGluR5, thus this will supply a new train of thought to cure pulp disease.Methods:1. Human premolars and third molars (n=5) that were extracted for orthodontic or treatment needs from patients at the Department of Oral Surgery, Shan Dong University Oral Hospital, were collected. Acute pulpitis (n=5)and chronic pulpitis(n=5)were defined clinically and pathologically. Serial tissue sections were cut for HE staining, immunohistochemical staining and PBS negative control respectively.2. The results of immunohistochemestry analysis:Digital image processing was used to analyse the expression of mGluR5. The optical density(OD)of the normal and inflammatory pulps were obtained by means of semi-quantitation in five random highpower fields of each section.3. SPSS software statistical treatment:Data was analyzed by ANOVA and LSD methods, and expressed as the means±SD. Value of P<0.05 was considered statistically significant.Results:1. The results of naked eyes observing:Healthy pulps are colorful and sheen. The healthy pulps are solid and flexible. The pulps are easily exfoliated from sclerous tissues. While the solidity of inflammatory pulps are small and brittleness to part.2. HE stanining results:The odontoblasts in normal cornal pulps are longitudinal, in the cervical and mid-coronal regions of the pulp are cubical, while in the root of the pulps are flat. The odontoblast layer is destroyed and the major chronic inflammation cells are lymphocytes in the chronic pulpitis tissues. The odontoblast layer is destroyed seriously and neutrophils are infiltrated around blood vessels in acute pulpitis tissues. The blood vessels in pulpitis tissues expand resulted in increasing permeability, so fluid exudation and tissue edema appear.3. Results of Immunohistochemistry:The expression of mGluR5 is positive in the whole normal pulp and the cornal of inflammatory pulp, while the expression of mGluR5 shows significantly weaker from cornal, cervical portion to root of normal pulp in turns, the expression of mGluR5 shows a significantly weaker from cornal of normal pulp, acute pulpitis to chropic pulpitis in turns.4. Analysis of the values of ODs in Immunohistochemistry:mGluR5 shows a significantly(P<0.05) weaker expression from cornal, cervical portion to root of normal pulp in turns. mGluR5 shows a significantly (P<0.05) weaker expression from cornal of normal pulp, acute pulpitis to chropic pulpitis in turns.Conelusions:1.mGluR5 shows a significantly weaker expression in turns from cornal, cervical portion to root of normal pulps.2. mGluR5 shows a significantly weaker expression in turns from cornal of acute pulpitis,chropic pulpitis to normal pulps.3.The expression and distribution differences of mGluR5 in normal pulp and pulpitis suggest that it may play an important role in transduction of pulp nociceptive signals. A subtype-selective mGluR5 antagonist (MPEP) can be used to block pain. This will supply a new train of thought to treat pulpitis.