Calcium-binding proteins in the dorsal ventricular ridge of the lizardPsammodromus algirus

Abstract

The aim of the present work was to study further the intrinsic organization of the dorsal ventricular ridge of lizards. For that purpose, the morphology and distribution of cells and fibers containing the calcium‐binding proteins calbindin‐D28k, parvalbumin, and calretinin were investigated by using immunohistochemical methods. Colocalization of calcium‐binding proteins with the neurotransmitter γ‐aminobutyric acid (GABA) was also studied because they are shown to coexist in many areas of the telencephalon where they define distinct subpopulations of GABAergic local circuit neurons. Neurons containing calcium‐binding proteins are limited to the anterior part of the dorsal ventricular ridge (ADVR), whereas the posterior or caudal portion of the ridge is devoid of immunoreactive cells. This result gives further evidence for defining both regions of the dorsal ventricular ridge. Calcium‐binding proteins mark three distinct populations of neurons within the ADVR. Two of them, parvalbumin‐ and calretinin‐expressing cells, are GABAergic. On the other hand, calbindin‐containing neurons do not express GABA, and the possibility is discussed that these cells are projection neurons. The distribution and overall density of fibers immunoreactive to calcium‐binding proteins suggests that most fibers are of extrinsic origin, the thalamic nuclei projecting to the ADVR and the lateral amygdala being good candidates for their origin. The comparison of data on the populations of calcium‐binding protein‐containing neurons in the reptilian ADVR with those of mammals illustrate the difficulty in finding a mammalian homologue for this controversial region of the reptilian telencephalon. J. Comp. Neurol. 405:32–44, 1999. © 1999 Wiley‐Liss, Inc.

Expression of calcium-binding proteins in the diencephalon of the lizardPsammodromus algirus

“…One aim of the present work is to provide a comprehensive study of the distribution pattern of calbindin-D28k (CB), calretinin (CR), and parvalbumin (PV) in the diencephalon of the lacertid lizard Psammodromus algirus, a species in which we already studied a number of cyto-and chemoarchitectonic aspects in the telencephalon (Dá vila et al, 1991(Dá vila et al, , 1993(Dá vila et al, , 1995(Dá vila et al, , 1997Guirado et al, 1999). These calcium-binding proteins are highly conserved in vertebrates and have been shown to be useful morphological markers that label specific neurons or circuits in brains of both mammals (Celio and Heizmann, 1981;Jones and Hendry, 1989;Hendry et al, 1989;Celio, 1990;Andressen et al 1993) and nonmammalian vertebrates (Braun, 1990;Dá vila et al, 1993Dá vila et al, , 1997Dá vila et al, , 1999De Castro et al, 1998;Guirado et al, 1999;Milá n and Puelles, 2000).…”

“…These calcium-binding proteins are highly conserved in vertebrates and have been shown to be useful morphological markers that label specific neurons or circuits in brains of both mammals (Celio and Heizmann, 1981;Jones and Hendry, 1989;Hendry et al, 1989;Celio, 1990;Andressen et al 1993) and nonmammalian vertebrates (Braun, 1990;Dá vila et al, 1993Dá vila et al, , 1997Dá vila et al, , 1999De Castro et al, 1998;Guirado et al, 1999;Milá n and Puelles, 2000).…”