Increasing evidence suggests that a major component of the inflammatory actions of prostaglandins is through augmenting the activity of small diameter sensory neurons. This activation and the subsequent release of neuropeptides from these neurons results in neurogenic inflammation and enhanced pain sensation. The studies outlined in this proposal will determine which prostaglandin receptor subtypes mediate sensitization of sensory neurons. The investigators will also examine the effects of inflammation and long-term exposure to inflammatory mediators on the expression and function of prostaglandin receptor subtypes. Finally, studies will elucidate the role of calcium/calmodulin dependent protein kinase in mediating sensitization after acute and long term exposure to prostaglandins. Alterations in receptor expression and function will be studied using two experimental models, 1) rat sensory neurons grown in culture and 2) spinal cord slices and dorsal root ganglia(DRGs) from rats with unilateral inflammation. The former model provides a unique opportunity to examine the mechanisms of eicosanoid action on sensory neurons without significant interference from other types of cells, whereas the latter affords the opportunity to study eicosanoid actions at the level of sensory input to the spinal cord during chronic inflammation. To assess receptor expression real time PCR detection, radioligand binding and immunoblotting will be used. To establish a causal relationship between activation of receptor subtypes and the sensitizing actions of prostaglandins, antisense technology will be used to reduce expression of specific receptor subtypes. The ability of prostaglandins to augment evoked release of substance P and calcitonin gene-related peptide from sensory neurons and to increase cAMP will be used as indices of sensitization. These studies will provide basic information as to the mechanisms of eicosanoid actions on sensory neurons and establish which prostaglandin receptor subtypes are important in altering neuronal sensitivity during inflammation. This knowledge is critically important for understanding the process of neurogenic inflammation and in ultimately designing new drug therapies for the management of inflammatory diseases.
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