The development of radial glia and astrocytes in the telencephalon of the lizard Gallotia galloti was studied by immunohistochemistry with anti-vimentin and anti-GFAP antibodies. Vimentin appears at embryonic stage 32 (E32) in the proliferative zone of the lateral ventricle and subpial end-feet in the marginal zone. At E34-35 the staining intensity for vimentin in all radial glia is maximal. It then decreases and disappears in most structures in adult animals. GFAP appears at E35 in the end-feet in the marginal zone and its intensity increases until adulthood, particularly in radial and sinuous fibers and in fibers that originate from the sulci and invade the ventral striatum and the septum. In contrast, the reaction is weak in the cortex, in the anterior dorso-ventricular ridge, and in the amygdala nuclei. Radial glia is still present in the adult, and the composition of its intermediate filaments changes during development from vimentin to GFAP. No GFA-positive cell bodies except those of ependymal glia were detected in telencephalon.

The distribution of glial fibrillary acidic protein (GFAP)- and vimentin-containing cells was studied by immunohistochemistry in the midbrain of the lizard Gallotia galloti. At embryonic stage 32 (E32), vimentin immunoreactivity appeared first in cell bodies located in the ventricular walls, in radial fibers, and subpial end-feet and increased in these structures until E34/E35. Faint GFAP immunoreactivity gradually appeared in the same structures between E34 and E37, and this increased until adulthood, whereas vimentin immunoreactivity decreased after E35, becoming limited to a few end-feet and fibers in the adult, mainly in the tegmentum. Thus, in developing Gallotia midbrain a shift from vimentin-containing to GFAP-containing intermediate filaments begins around E36 or E37. At E40, in addition to the cell bodies in the ependymal area, dispersed GFAP-positive cells, possibly immature astrocytes appeared. These cells showed the same shift. In the adult lizard, GFAP-positive radial glia are still present and coexist with GFAP-positive astrocytes, which are prefentially located in the marginal optic tract and the oculomotor nuclei, but are absent in the fasciculus longitudinalis medialis. Optic tectum, pretectum, tegmentum, and isthmic nuclei are the areas richest in GFAP-positive radial fibers: these were much less abundant in the deep mesencephalic nuclei. Thus, in this lizard, GFAP-positive astrocytes display a clear cut regional distribution: they are present in mesencephalon, whereas they are absent in telencephalon.

The projection pattern of the ventral thalamic reticular nucleus onto the dorsal thalamus was studied in the lizard Gallotia galloti using in vitro horseradish peroxidase and fluorescent carbocyanine labelling techniques. Localized label deposits at three dorsoventrally spaced sites in the dorsal thalamus elicited retrograde transport into separate, though partly overlapping, medial, dorsolateral and ventrolateral sectors within an extended cytoarchitectonic complex which may be globally identifiable as the reticular nucleus. Neurons found in the dorsolateral and ventrolateral sectors mainly corresponded to the cell group named nucleus ventromedialis (or nucleus of the dorsal supraoptic decussation) in the literature, whereas neurons labelled in the medial sector corresponded to the so-called dorsal hypothalamic nucleus. Sparser cells appear labelled in the superficially placed nucleus suprapeduncularis. Thalamotelencephalic fibers arising from the injected dorsal thalamic nuclei also project to the corresponding retrogradely labeled sectors within the reticular nucleus. These findings reveal a rough topographic organization in the connections of the extended reticular nucleus complex with the whole dorsal thalamus. This supports the hypothesis of hodological homology between this ventral thalamic formation in Gallotia and the mammalian thalamic reticular nucleus.

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