Journal of Neuroscience, Vol 3, 1760-1772, Copyright © 1983 by Society for Neuroscience
Development of motor innervation of the chick following dorsal-ventral limb bud rotations
BA Ferguson
To test mechanisms which motoneurons may use to grow to their appropriate
targets, I rotated the limb around the dorsal-ventral axis prior to
motoneuron outgrowth. The positions of motoneurons in the spinal cord
innervating individual muscles and muscle masses were then determined using
retrograde horseradish peroxidase uptake. Motoneurons innervated their
appropriate muscles after dorsal-ventral limb rotation, before and after
motoneuron death. Thus, cell death does not serve to remove errors in
matching between motor nuclei and their corresponding muscles after
dorsoventral rotation of the limb. Motoneurons must be specified for a
peripheral target prior to outgrowth, and they grow to that target
relatively directly. Axons compensated for the limb rotation by first
collecting into groups in a position appropriate for the normal limb
orientation, then shifting dorsal-ventral position within the plexus and
proximal nerve trunk. Based on these results it is hypothesized that axons
destined to innervate dorsal or ventral musculature might use chemospecific
cues during growth to maintain appropriate positions within the nerve with
respect to limb orientation.