The intent of the proposed research is to increase our understanding of pain processing in the trigeminal system, to compare this with organization in spinal nociceptive pathways, and to provide anatomical insights regarding the afferent component of the sensorimotor reflex arc in orofacial reflexes. Functionally identified trigeminal primary afferent fibers will be intracellularly stained with horseradish peroxidase (HRP). Axons innervating periodontal ligament, pulpal and oral structures will be of principle concern. The location of these fibers in the trigeminal tract, the frequency and trajectory of collateral branching, the terminal arborization pattern and the nature of primary afferent synaptic contacts will be analyzed with both light and electron microscopic techniques. While evaluation of the motor component in orofacial reflexes is beyond the scope of this proposal, one long range goal is to investigate mechanisms which mediate the integration of sensory information with reflexive and/or voluntary motor output. Clinical symptoms such as myofacial pain and muscle spasm of splinting often appear to incorporate both sensory and motor elements during the course of the disease process. This is interesting when considering the etiologies of such dysfunctions vary from trauma to occlusal disharmony and temporomandibular joint (TMJ) pathosis. A better understanding of the organization of sensory and sensorimotor pathways in the trigeminal system can only lead to more effective management of such clinical dysfunction. Concomitantly with the research project, an integrated training program in Neurophysiology leading to the PhD degree and in Orthodontics leading to specialty board eligibility will be carried out. The clinical program relates to the basic science program through its emphasis on care for patients with dysfunction of the stomatognathic system. The long term objective is to produce a clinical scientist working in this field.
