The lacteridian reticular thalamic nucleus projects topographically upon the dorsal thalamus: Experimental study in Gallotia galloti

Abstract

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.

Reelin mRNA expression during embryonic brain development in the turtleEmys orbicularis

“…Surrounding these differentiating fields, however, a layer of strong reelin expression formed a perirotundal belt. This reelin-positive zone became particularly large and prominent in more ventral thalamic areas, corresponding to the reticular thalamic complex (as described in Diaz et al, 1994). The lateral part of the ventral thalamus contained a large, well-labeled nucleus that was most likely the ventral division of the lateral geniculate complex (Fig.…”

“…Similarly, in the ventral thalamic complex, several nuclei, such as the area triangularis and nucleus ovale, were negative. By contrast, there was robust expression in some ventral thalamic components, such as the ventral division of the lateral geniculate nucleus and a broad zone corresponding to the future suprapeduncular, ventrolateral, and ventromedial thalamic nuclei, which are considered homologous to the mammalian reticular thalamic nuclei (Diaz et al, 1994). In the hypothalamus, nuclei located in periventricular position were diffusely but clearly labeled, whereas a few neurons scattered more laterally and not disposed into clearly defined nuclei showed moderate expression.…”

Prosomeric map of the lamprey forebrain based on calretinin immunocytochemistry, nissl stain, and ancillary markers

“…Cells immunoreactive to cone opsin and ␣ -transducin antisera have been specifically found in the dorsal tier of the dorsal thalamus (pars subhabenularis of Schober, 1964;García-Ferná ndez et al, 1997). Though dorsoventral tiers in the dorsal thalamus have been recognized before in sauropsids (Martínez-de-laTorre, 1985;Díaz, 1992;Díaz et al, 1994, their Fig. 7; Puelles, unpublished data), they were not obvious with AChE histochemistry in the frog (Puelles et al, 1996).…”

Thalamic Reticular Nucleus in <b><i>Caiman crocodilus</i></b>: Immunohistochemical Staining

“…In some lizards, such as Gallotia galloti, 3 nuclei comprise the thalamic reticular nucleus: nucleus dorsolateralis hypothalami, nucleus ventromedialis (which has a dorsal and ventral component), and nucleus suprapeduncularis [Díaz et al, 1994]. This same nomenclature was used in an immunohistochemical study in another lizard group, Psammodromus algirus [Dávila et al, 2000].…”

“…In reptiles, a nucleus that lies within the fibers of the lateral forebrain bundle [Adams et al, 1997] shares several properties with the thalamic reticular nucleus of mammals [Díaz et al, 1994;Kenigfest et al, 2005;Pritz, 2016a]. In crocodilians, this neuronal aggregate was termed the thalamic reticular nucleus [Pritz and Stritzel, 1990].…”