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Published April 1986 | public
Journal Article

Dynamic Aspects of Retinotectal Map Formation Revealed by a Vital-Dye Fiber-Tracing Technique

Abstract

In the visual system of Xenopus laevis, the axons from the retinal ganglion cells of the eye form a topographic projection onto the optic tectum. Many studies have focused on revealing the mechanisms responsible for this precise and regular projection pattern. In contrast to the static view of the system that one might expect from examining the regularity of the projection, recent work on its regeneration and its changes during larval development indicate that part of the patterning process involves the dynamic behavior of optic fibers. Typically, anatomical and electrophysiological techniques have been used to obtain static views of the developing retinotectal projection which then must be compiled to provide a glimpse of any dynamic behavior. Here we report on experiments using a newly developed fiber tracing technique to directly follow the emergence of topography in the developing retinotectal projection. Defined halves of the developing eyebud were labeled with a vital fluorescent dye which fills the growing axons, and the projection of the labeled cells was followed for up to 2 weeks in individual animals. The experiments confirm that dorsal and ventral optic nerve fibers sort out into an ordered projection early in development. In contrast, nasal and temporal fibers initially overlap, and the same sets of prelabeled fibers then sort out into the adult topography over a period of days.

Additional Information

© 1986 Academic Press, Inc. Received March 1, 1985; accepted in revised form November 4, 1985. We thank J. Braun and R. Gimlich for their generous gifts of some of the fluorescently labeled dextrans used in these experiments, V. Bayer for assistance in preparing nerve cultures, D. Valentino and L. Belluzi for help with histology, and M. Bronner-Fraser, J. Coulombe, and D. Krotoski for their comments on the manuscript. This work was supported by grants from the NSF (BNS80-23638 and BNS84-06307) and by a McKnight Foundation Scholar's Award.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023