J. Comp. Neurol. 438: 1-11 (2001)
Development of GABA-immunoreactive neuron patterning in the spinal cord.
E. Binor & R. D. Heathcote
In the frog Xenopus
laevis, GABA-immunoreactive spinal cord neurons (Kolmer-Agduhr cells) formed
a dispersed pattern within two columns on either side of the midline.
The cellular pattern became established during embryonic and larval
development. The GABA-immunoreactive cells are cerebrospinal fluid (CSF)-contacting
neurons that began to appear by 1.2 days (st 26) of development.
This occurred shortly after neural tube closure (0.9 days, st 21) and
followed the appearance of ultrastructural characteristics of CSF-contacting
neurons. The pattern of GABA-immunoreactive
cells emerged during embryogenesis, as their density increased.
Each longitudinal column was heterogeneous, containing cells with and
without GABA immunoreactivity. Spatial
analysis at several embryonic and larval stages showed that the cells in each
column formed a nonrandom, dispersed pattern even at early stages of
differentiation. This one-dimensional pattern resembled that of
dopamine-immunoreactive neurons, which are also located in the ventral spinal
cord. The patterning of both cell
types followed a different time course, but the ultimate spacing of the neurons
remained comparable. These results suggested that the mechanism patterning the two
cell types within the same region was similar but not identical and may involve
related molecular mechanisms.