Hippocampal pyramidal cells: the reemergence of cortical lamination.
Bottom Line: Distributions of deep and superficial pyramidal cell dendrites and studies in reeler or sparsely GFP-expressing mice indicate that this also applies to afferent pathways.Histological, neurochemical, and connective differences between deep and superficial neurons may correlate with (patho-) physiological phenomena specific to pyramidal cells at different radial locations.We feel that an appreciation of radial subdivisions in the pyramidal cell layer reminiscent of lamination in other cortical areas may be critical in the interpretation of studies of hippocampal anatomy and function.
Affiliation: Institute of Anatomy, University of Zürich, 8057 Zürich, Switzerland. email@example.comShow MeSH
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Mentions: Calbindin. The distribution of calbindin immunoreactive (CaBP-ir) pyramidal cells in CA1 of the rat hippocampus probably represents the earliest neurochemical evidence for a radial subdivision of the layer. Throughout most of the transverse extent of the layer, CaBP-ir pyramidal cells are located in the cell-dense superficial part, while deeper pyramidal cells do not contain this protein (Baimbridge and Miller 1982; Rami et al. 1987b; Sloviter 1989; Celio 1990). In the septal hippocampus, CaBP-ir pyramidal cells form a superficial mono- or bilayer above unstained deeper cells (Fig. 4c; also compare with Fig. 2l, m). Only at the proximal limit of CA1, where CaBP-ir becomes weak superficially, CaBP-ir appears in some of the deepest pyramidal cells. The deepest cells are also stained distally, in the vicinity of the subiculum. Baimbridge et al. (1991) have shown that there was virtually no overlap in the labeling of CaBP-negative and CaBP-ir pyramidal cells when animals were injected with 3H-thymidine on E16 and E18, respectively. Notably, calbindin expression is apparently controlled by Zbtb20—being down-regulated in cells in which the expression of Zbtb20 has been blocked and appearing in deep pyramidal cells as the expression of Zbtb20 is induced in these cells (Nielsen et al. 2010). Despite their change in location, pyramidal cells in CA1 of reeler mice retain their identities with regard to calbindin expression, which is strongest in the deep sublayer but weak or absent in superficial cells (Fig. 3d).Fig. 4
Affiliation: Institute of Anatomy, University of Zürich, 8057 Zürich, Switzerland. firstname.lastname@example.org