Afferent axonal pathfinding in developing chicken rhomboencephalon

Author: Kubke, Maria; Wild, JM

Date: 2008

Type: Conference poster

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The University of Auckland Library


The developing hindbrain of vertebrates i organized in a series of rhombomeres, each giving rise to specifi c nuclei. The role of this segmentation has been extensively studied with respect to the origin of motor nuclei. The development of afferent innervation, however, has received little attention. Afferent axons enter the brainstem prior to the migration of their central targets and must therefore navigate in the absence of target derived information. Since the target nuclei for each afferent component originates within discrete rhombomeric boundaries, it is possible that the same positional information that is used by neuronal progenitors to defi ne their fi nal fate, may be available to afferent axons to direct them through their initial growth. This study was aimed at determining the normal sequence that characterises the growth of afferent axons in the hindbrain within the context of the site of origin and of the organisation of second order sensory neurons within specifi c rhombomere boundaries. Afferent axons were labelled at different embryonic ages using fl uorescent lipophilic dyes. Crystals of DiI and/or DiO were placed on specifi c exposed nerves or nerve branches of fi xed embryos. Embryos were incubated at 30 C for 18 hrs, after which the hindbrains were dissected, cleared in glycerol and analysed as whole-mount preparations with confocal microscopy. Afferent axons formed a series of fascicles that extended longitudinally along the alar plate, beyond the rhombomeric boundaries that give rise to their target nuclei. At early stages, the degree of organization and segregation of afferent axons did not appear to refl ect the adult patterns. Thus, it appears that the appropriate pathfi nding and fi nal segregation of the afferent components involves an initial profuse growth into the hindbrain, and that proper afferent patterning involves axon retraction and may require the initiation of migration if the central targets towards their fi nal position.

Citation: ["26th International Australasian Winter Conference on Brain Research. 2008"]