Reinnervation following sparse regeneration

University Of California Irvine, Irvine CA

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Abstract

DESCRIPTION (provided by applicant): When the optic nerve of an adult goldfish is severed, optic fibers will grow back to the optic tectum, their primary termination site, to reestablish optic connections. With time, the retinotopic precision of this regenerated projection becomes indistinguishable from normal. In adult mammals, optic and other CNS axons do not normally regenerate. However, efforts to promote regeneration have met with limited success. Regeneration past the injury zone, formation of connections and restoration of some function have been achieved. Unfortunately, the number of fibers that regenerate in mammals are relatively sparse. The consequences of having low numbers of regenerating fibers on their capacity to reform accurate connections is largely unknown. To explore this question, the present study asks how well optic fibers in the goldfish reform ordered connections when their number is greatly reduced. The approach will utilize a surgical method developed in this laboratory wherein a controlled number of fibers ranging from a few percent to 40-50 percent of retina will be redirected from one tectum into the opposite host tectum. The host tectum will be denervated of optic fibers by removing its contralateral eye at various times prior to this "deflection." The formation of the low density projection will be analyzed by anatomical, in vivo imaging and electrophysiological methods.