Early neuronal development in the spinal cord of a reptile assessed by neurofilament protein immunoreactivity.

The neural tube in the Gallotia galloti Stage 22 (S.22) embryo is already closed at the level of the cervical flexure, while caudal closure does not end until S.23. Cell proliferation begins shortly after the final neural tube closure, being rapid and giving rise, by S.26, to a thick ventricular zone. Cell migration does not start until S.28, initially in the basal plate, and forming putative motoneurons. Migration in the alar plate does not start until S.33. The appearance of the first neurofilament protein-positive perikarya coincides with the structural and ultrastructural identification of the neuron, although neurofilament-immunoreactive cells can already be identified inside the ventricular zone. Finally, from S.35 onwards, after major cell migration has already occurred, neuronal maturation continues in situ.