Journal of Neuroscience, Vol 13, 4898-4907, Copyright © 1993 by Society for Neuroscience
Preganglionic autonomic motor neurons display normal translocation patterns in slice cultures of embryonic rat spinal cord
RP Barber, PE Phelps and JE Vaughn
Division of Neurosciences, Beckman Research Institute of the City of Hope, Durate, California 91010.
Phenotypic differences between somatic and autonomic motor neurons (SMNs
and AMNs, respectively) may be modulated by epigenetic factors during the
histogenic migrations of these cells. In order to study this problem
experimentally, we have developed an in vitro, organotypic slice
preparation of embryonic rat spinal cord. Our main objectives for this
preparation were to determine whether in vivo patterns of motor neuronal
translocations were mimicked in vitro, and, if they were, to begin to
analyze such movements with experimental procedures that cannot be applied
to the study of mammalian spinal cord development in vivo. Using a
modification of existing organotypic slice procedures, we have shown that
ChAT, an axonal surface glycoprotein and a low- molecular-weight
neurofilament protein are expressed in slices cultured for up to 21 d, thus
indicating that spinal neurons remained viable in vitro for relatively long
periods. Most importantly, retrograde labeling and subsequent confocal
microscopy have shown that the SMNs and AMNs of the slice preparations
become segregated ventrodorsally into two distinct subcolumns as seen in
vivo. The formation of separate AMN and SMN subcolumns appears to result
from a dorsal translocation of AMNs. The fact that this cellular movement
occurs in the slice preparation has allowed us to follow this phenomenon
directly within the same specimen over a period of days. In addition, we
have been able to observe the translocation of AMNs following the removal
of their peripheral synaptic targets. The results of these experiments
provide further evidence that AMNs undergo a dorsal translocation during
the course of spinal cord development, and that this cellular movement may
be due to an active migration. They also indicate that AMN movement is not
dependent upon continual connection of these neurons with the paravertebral
sympathetic ganglia.