INNERVATION OF THE MAXILLARY SINUS IN RATS

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Greater than twenty percent of Americans (in 1991, over 50 million people) suffer from chronic inflammation of the nasal and sinus mucosa. These various inflammatory disorders are collectively grouped under the term rhinosinusitis. One of these disorders, allergic rhinitis, alone results in over 28 million restricted days, 6 million bedridden days, 5 million work-loss and school-loss days, and over one-half billion dollars in physician and drug expenses each year (from a national survey reported in 1975). Inflammation of the upper respiratory system clearly is a major problem for many people in the United States. The major specific aim of this preliminary research is to develop a greater understanding of the innervation of the nasal cavity and the paranasal sinuses in the rat. A second specific aim is to develop a model of inflammation in the rat's nasal cavity and paranasal sinuses. Determining the central projections of the nerves innervating the nasal cavity and maxillary sinus will be accomplished by placing cotton pledgets soaked in horseradish peroxidase conjugated to wheat germ agglutin (WGA- HRP) into the nasal cavity and the maxillary sinus. WGA-HRP is retrogradely transported by primary afferent axons to cell bodies located in the trigeminal ganglion; it then is transported transganglionically to terminals of the primary afferent fibers in the brain stem. In developing a model of rhinosinusitis in the rat, agents that have been used in other studies of inflammation will be used to determine the most appropriate one for use in the upper respiratory system. Many inflammatory agents injected into the hindpaw of the rat produce increases in opioid peptides localized to the lumbar spinal cord. Alterations in dynorphin in neurons located in the brain stem will be used to assess the extent of rhinosinusitis. In this model, increased dynorphin should be localized to areas of termination of the primary afferent fibers innervating the nasal cavity and paranasal sinuses. Two immediate benefits will result from this research. First, information describing the innervation of the nasal cavity and paranasal sinuses will provide the clinician with a more complete understanding of the reasons why different clinical pathologies often exhibit similar symptoms. For example, projections to the nucleus of the spinal trigeminal tract described in this research probably will overlap with projections, already described in the literature, from other structures. This convergence of different central projections may provide an explanation for the difficulty patients have in localizing different facial pains. Second, developing a model of rhinosinusitis in the rat to help evaluate the role of the nervous system in this inflammatory process will lead to pharmacological interventions, which are both safer and more effective than those available currently, for the treatment of rhinosinusitis.