Heterogeneous Immunoreactivity of Glial Cells in the Mesencephalon of a Lizard: A Double Labeling Immunohistochemical Study

ABSTRACT Astrocytes and radial glia coexist in the adult mesencephalonof the lizard Gallotia galloti . Radial glia and star-shaped astrocytes expressglial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). Thesame cell markers are also expressed by round or pear-shaped cells that aretherefore astrocytes with unusual morphology.Other round or pear-shaped cells, also scattered in the tegmentum and thetectum, display only GS. Electron microscopy reveals that these cells may beoligodendrocytes. In this lizard, the GS is expressed in some oligodendrocyteswhile this does not occur in the central nervous system of mammals in situ.These results confirm that the cellular specificity of GS is different in variousspecies and suggest that ependymal cells are also immunoreactive for GS buttheydonotcontainGFAP.J.Morphol. 235: 109–119,1998. r 1998 Wiley-Liss, Inc.KEY WORDS: glial cells, mesencephalon, astrocytes, immunohistochemistry, glial fibrillary acidicprotein Radial glia (RG), a primordial form of gliain phylogeny and ontogeny, disappears dur-ing ontogeny in mammals, while they are apermanent feature in the central nervoussystem(CNS)ofnonmammalianvertebratessuch as reptiles.Using immunohistochemistry with anti-bodies that recognize the astrocyte-specificglialfibrillaryacidicprotein(GFAP),wehavepreviously shown (Monzo´n-Mayor et al.,’90a,b; Yanes et al., ’90) that in the lizard