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Chick wing innervation. III. Formation of axon collaterals in developing peripheral nerves
1Department of Biology, Bryn Mawr College, Pennsylvania 19010, USA.
The Journal of Comparative Neurology
|June 26, 1995
Summary
Early in chick embryo limb development, axons can branch into multiple nerves. These connections, called two-nerve collaterals, are common in forming nerves but disappear by later stages.
Area of Science:
- Neuroscience
- Developmental Biology
- Embryology
Background:
- Axon navigation in vertebrate limb development involves growth cone changes and branching.
- Previous work noted terminal axon branching during limb innervation.
Purpose of the Study:
- To investigate if axon branching extends to projections into different peripheral nerves.
- To characterize the formation and fate of collateral projections between nerves during limb development.
Main Methods:
- Horseradish peroxidase or Dil injections into peripheral nerves of chick embryos (stages 28-35).
- Tracing of labeled axon trajectories proximally to identify collateral projections.
- Analysis of collateral distribution along proximodistal and anteroposterior limb axes.
Main Results:
- Collaterals projecting into uninjected nerves were frequently observed during early nerve formation (stages 28-29).
- These two-nerve collaterals occurred in both motor and sensory axons, connecting adjacent limb regions.
- The frequency of two-nerve collaterals decreased significantly by stage 32 and were absent by stage 33.
Conclusions:
- Axons initially project to multiple nerves during vertebrate limb development.
- Two-nerve collateral projections are transient, diminishing as limb innervation progresses.
- The mechanism for the elimination of these early collateral connections remains unknown.