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Title: ATP and ATP receptors in human dental pulp
Author: Alavi, Atossa Maryam
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2003
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There is accumulating evidence that ATP may play a role in the initiation of pain by acting on P2X3 receptors expressed on nociceptive afferent nerve terminals. The aim of this study was to examine whether ATP and its receptors play a role in pain mechanisms in the human dental pulp by i) immunohistochemical staining of pulp tissue with antibodies to P2X3 receptors; and ii) by exploring whether odontoblasts release ATP. The presence, distribution and colocalisation of P2X3 receptors with other neural markers was investigated in human dental pulps. Pulps were removed from extracted third molars and stained with human anti-P2X3 antibody. P2X3 -immunoreactive (-ir) nerve fibres were detected in the main body of the pulp, in the subodontoblastic plexus of Raschkow and on nerve fibres projecting in between odontoblasts. Double labelling with anti-P2X3 and anti-neurofilament showed that the majority (but not all) fibres in the pulp, including both myelinated and unmyelinated nerve fibres, express P2X3 receptors. Double labelling with isolectin B4 (IB4) and anti-P2X3 showed that all P2X3-ir nerves also bind IB4. Therefore, both small and medium sized nerve fibres in the human pulp express P2X3 receptors. The possibility that odontoblasts could be potential sites for ATP release was studied using an in-situ method of odontoblast culture in 14 freshly extracted human third molars. Using this model, it was possible to directly stimulate the layer of odontoblasts still attached to dentin. The amount of ATP present in the solution bathing the odontoblasts was measured after stimulating the cells with hypo-osmotic solutions, ATP, and mechanical stimulation. Cell lysis was measured as each data point using a lactate dehydrogenase assay. Active ATP release was calculated by subtracting the ATP released as a result of cell lysis from the total bulk ATP. Between 0.5-10 nM active ATP release was observed when odontoblasts were stimulated by a 16-18% hyposmotic solution or by mechanical stimulation. These numbers, however, most probably under-represent the amount of actual ATP released during cell stimulation. In conclusion, P2X3 receptors are present on both myelinated and unmyelinated nerve fibres in human dental pulp, these receptors are probably responsive to ATP released from odontoblasts and may play a role in dental pain mechanisms. The roles of extracellular ATP in dental pulp are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available