Anterior dorsal ventricular ridge in the lizard: Embryonic development

Abstract

In lacertids the telencephalic vesicle starts its development at stage E = 30, at which time it is lined by a homogeneous nucleated zone in which particular ventricular zone territories or sulci cannot be distinguished. At stage E = 32 coinciding with the initial development of the anterior dorsal ventricular ridge (ADVR), one may distinguish the ventricular zone b in the dorsolateral wall of the ventricle adjacent to the sulcus lateralis. The ADVR continues growing by incorporation of cells produced in two proliferative zones (zone b and wall of the sulcus lateralis) and appears fully developed in postnatal lizards. Ultrastructural characteristics of young ADVR neurons between stages E‐32 and E‐33 are typical of those in immature cells. Beginning at stage E‐34, some of these neurons appear to be degenerating (pycnotic). Thereafter, neurons of the ADVR develop abundant cytoplasmic organelles and the neuropile grows quickly. Myelination starts in the ADVR between stages E‐38 and E‐40, but is not observed in other striatal masses in the same period. Vascularization begins and is well developed at E‐40. The first synaptic contacts were observed in embryos of stage E=38; they are chiefly axo‐dendritic, although some are axo‐somatic. Degenerating neurons were found in the ADVR up to hatching. From stage E‐40 onward, the ADVR shows a greater and more rapid differentiation than all other striatal nuclei, including the ventral and amygdaloid complex. Copyright © 1987 Wiley‐Liss, Inc.