ROLE OF INNERVATION IN ELECTRORECEPTOR REGENERATION

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The tuberous electroreceptors of weakly electric fish are related to hair cells of the lateral line and inner ear. Like some hair cells, they are tuned by an electrical filter in their basal membranes. The number of sensory cells in each organ increases throughout the fish's life, the new sensory cells being produced by support cells. Furthermore, after skin has been removed new skin regrows in the wound and tuberous receptor organs regenerate, we believe, from the support cells of intact organs in the surrounding skin that migrate into the regenerating skin. During regeneration the tuberous organ begins as a layer of support cells around a lumen, and these support cells also give rise to the new sensory cells. These receptors show a dependence on their innervation in that receptor organs become disrupted and lose sensory receptor cells 2-3 weeks after denervation. Receptor organs also do not appear in denervated skin. We wish to answer the following questions in this proposal. 1) Does receptor cell tuning change after denervation? 2) What morphological changes occur in receptors as they degenerate and what changes, if any, occur in the support cells? 3) What role does innervation play in stimulating support cells to become mitotic and add new sensory cells in intact organs? 4) What role does innervation play in the early regeneration of tuberous sensory organs and, do organs regenerate if the new skin is surrounded by old organs that are denervated? 5) Are newly regenerated organs especially sensitive to denervation? 6) How do rates of mitosis change in support cells of regenerating organs after denervation? The results from this study will increase our fundamental understanding of the process of sensory cell regeneration and the putative trophic influence of afferent nerves upon their sensory cells.