The Journal of Neuroscience, December 15, 1998, 18(24):10473-10480
Segmental Specificity of Chick Sympathetic Preganglionic
Projections Is Influenced by Preganglionic Neurons from Neighboring
Spinal Cord Segments
Joseph W.
Yip,
Yee Ping L.
Yip, and
Christine
Capriotti
Department of Neurobiology, School of Medicine, University of
Pittsburgh, Pittsburgh, Pennsylvania 15261
Sympathetic preganglionic neurons of the chick are located between
the brachial and lumbosacral enlargements of the spinal cord. Their
axons exit the spinal cord via their adjacent ventral roots and project
rostrally or caudally along the sympathetic trunk to innervate
sympathetic ganglia. The projections of sympathetic preganglionic
neurons are segmentally specific. Neurons from the 16th cervical (C16)
and the first thoracic (T1) spinal cord segments project predominantly
in the rostral direction, whereas those from the fifth thoracic (T5) to
the first lumbar (L1) spinal segments project predominantly in the
caudal direction. Neurons from intervening spinal cord segments
(T2-T4) project in rostral and caudal directions. In the present
study, neural tube manipulations show that the direction of
preganglionic projections is altered by both the elimination and
addition of preganglionic neurons projecting into the sympathetic trunk
from neighboring segments. The present study also compares the
projections of preganglionic neurons from transplants of multiple
neural tube segments with those from transplants of single neural tube
segments reported in a previous study (). In the previous
study when single thoracic neural tube segments were transplanted to
the cervical level, preganglionic neurons did not maintain their
original projection patterns. The present study found that, when
contiguous neighboring segments were transplanted to the cervical
level, preganglionic neurons maintained projection patterns
characteristic of their original segmental levels. These results
indicate that the direction of preganglionic projections can be
influenced by neurons from neighboring segments, suggesting that the
formation of segmentally specific preganglionic projections during
embryogenesis may involve the interactions of preganglionic neurons
with those from neighboring spinal cord segments.
Key words:
axon guidance; competition; transplantation; autonomic
neurons; chick embryo; neuronal interactions
Copyright © 1998 Society for Neuroscience 0270-6474/98/182410473-08$05.00/0