![]() Pyramidal cells give rise to a long, thick apical dendrite and several minor basal dendrites that emerge from the apex and base of the teardrop-shaped soma, respectively. Pyramidal cells in the Ammon’s horn (cornu ammonis, or CA) and granule cells in the dentate gyrus (DG) are the two principal neuronal types in the hippocampal formation, exhibiting distinct dendritic arbor structures. Neurons of the central nervous system exhibit enormously diverse dendritic arbor architecture, which determines both the number and type of synaptic inputs received, and hence critically affect neuronal connectivity. The apical dendrite designation is determined from among multiple growing dendrites of young developing neurons. Our results suggest that polarized growth of the apical dendrite is regulated by cell intrinsic programs, while regression of basal dendrites requires cue(s) from the extracellular environment in the dentate gyrus. Before dendritic polarity was stabilized, the Golgi moved dynamically within the soma and was repeatedly repositioned at newly emerging principal dendrites. Time-lapse imaging revealed that up until the second week in culture, final principal dendrite designation was not stabilized, but was frequently replaced by other minor dendrites. Asymmetric growth of a single principal dendrite harboring the Golgi was observed in both cell types soon after the onset of dendritic growth. While basal dendrites in granule cells are normally degraded by adulthood in vivo, cultured granule cells retained their minor dendrites. Pyramidal and granule cells in culture exhibited similar dendritic patterns with a single principal dendrite and several minor dendrites so that the cell types were not readily distinguished by appearance. Furthermore, we observed and described the final apical dendrite determination during dendritic polarization by time-lapse imaging. Using quantitative morphometric analyses of mouse hippocampal cultures, we evaluated the differences in dendritic arborization patterns between pyramidal and granule cells. Both cell types form a long apical dendrite which extends from the apex of the cell soma, while short basal dendrites are developed only in pyramidal cells. Hippocampal pyramidal cells and dentate granule cells develop morphologically distinct dendritic arbors, yet also share some common features.
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