While central nociceptive effects of glutamate have been well characterized, relatively little is known about the potential peripheral effects of glutamate in activating terminals of certain primary afferent nociceptors. Such peripheral actions of glutamate would be physiologically and clinically significant, since activation of certain nociceptive primary afferent neurons could result in peripheral secretion of neuropeptides (contributing to neurogenic inflammation, and membrane depolarization (contributing to hyperalgesia). This proposal evaluates the hypothesis that the excitatory amino acid glutamate activates certain peptidergic neurons innervating dental pulp. In addition, the proposed experiments will evaluate the biochemical regulation of specific EAA receptors mediating this neuronal activation. The following specific aims are addressed: 1. Pharmacologically identify the receptor sub-type(s) mediating glutamate activation of pulpal sensory neurons. These studies will use isolated superfused dental pulp to determine the effects of glutamate, and related agonists to determine the effects of stimulating EAA receptors on evoking iCGRP release. 2. Biochemically identify the EAA receptor subunit composition in dental pulp and determine the cells which express the pulpal EAA receptor. We will use antisera selective to EAA receptor subunits to immunoprecipitate receptor complexes to identify pulpal EAA receptors. Additional studies will use in situ hybridization to determine expression of EAA receptor subunits, and immunocytochemistry to determine co-localization with iCGRP. 3. Determine the effects of injury-induced inflammation on binding properties and subunit expression of EAA receptors in dental pulp. These studies will evaluate the effect of pulpal exposure on the expression and subunit composition of EAA receptor subtypes in dental pulp, trigeminal ganglion, and other tissue. 4. Determine the peripheral source of glutamate released during pulpal inflammation. These studies will use microdialysis probes implanted in dental pulp to determine the effects of pulpal exposure on peripheral glutamate release. This proposal outlines a multi-methodological approach designed to characterize pulpal responses to the excitatory amino acid glutamate, specifically, its ability to modulate activation of peptidergic sensory neurons and the development of neurogenic inflammation. The extensive vascular and neural components of dental pulp make this an ideal tissue in which to study glutamate-evoked responses. An understanding to these mechanisms may have future utility in modulating the development of pulpitits in clinical patients.
| Jackson, D L; Hargreaves, K M (1999) Activation of excitatory amino acid receptors in bovine dental pulp evokes the release of iCGRP. J Dent Res 78:54-60 |
