Neurogenesis in the septal and temporal part of the adult rat dentate gyrus

Abstract

Structural and functional dissociation between the septal and the temporal part of the dentate gyrus predispose for possible differentiations in the ongoing neurogenesis process of the adult hippocampus. In this study, BrdU-dated subpopulations of the rat septal and temporal dentate gyrus (coexpressing GFAP, DCX, NeuN, calretinin, calbindin, S100, caspase-3 or fractin) were quantified comparatively at 2, 5, 7, 14, 21, and 30 days after BrdU administration in order to examine the successive time-frames of the neurogenesis process, the glial or neuronal commitment of newborn cells and the occurring apoptotic cell death. Newborn neurons' migration from the neurogenic subgranular zone to the inner granular cell layer and expression of glutamate NMDA and AMPA receptors were also studied. BrdU immunocytochemistry revealed comparatively higher numbers of BrdU(+) cells in the septal part, but stereological analysis of newborn and total granule cells showed an identical ratio in the two parts, indicating an equivalent neurogenic ability, and a common topographical pattern along each part's longitudinal and transverse axis. Similarly, both parts exhibited extremely low levels of newborn glial and apoptotic cells. However, despite the initially equal division rate and pattern of the septal and temporal proliferating cells, their later proliferative profile diverged in the two parts. Dynamic differences in the differentiation, migration and maturation process of the two BrdU-incorporating subpopulations of newborn neurons were also detected, along with differences in their survival pattern. Therefore, we propose that various factors, including developmental date birth, local DG microenvironment and distinct functionality of the two parts may be the critical regulators of the ongoing neurogenesis process, leading the septal part to a continuous, rapid, and less-disciplined genesis rate, whereas the quiescent temporal microenvironment preserves a quite steady, less-demanding neurogenesis process.

Distinct Properties of Long-Term Potentiation in the Dentate Gyrus along the Dorsoventral Axis: Influence of Age and Inhibition

“…The maturation of new granule cells in the ventral DG was shown to be slower 43, 44 , giving them a wider time window to express enhanced plasticity. Furthermore, although the net neurogenic capacity is similar between both regions, adult neurogenesis happens more continuously and less disciplined in the dorsal hippocampus 45 . Dorsal adult-born cells were shown to be crucial for contextual discrimination, whereas those in the ventral DG are required for anxiolytic effects 46, 47 .…”

Neurogenesis in the Developing and Adult Brain—Similarities and Key Differences

“…Calcium-permeable AMPA receptors containing a specific GluRA2 subunit (Whitney et al 2008) are expressed before the onset of NMDA receptors in more differentiating conditions (LoTurco et al 1991; Muth-Kohne et al 2010a). In the adult SGZ, although proliferating cells express NMDAR1 and AMPA GluR2 subunits (Bekiari et al 2015), aNSCs were originally reported as responding to GABA but not to glutamate stimulation (Tozuka et al 2005). However, this apparent functional absence of responsiveness to glutamate may be because of the fact that receptor agonists were applied to the soma of aNSCs (Tozuka et al 2005) and not to their tufted processes that was only recently reported to harbor AMPA/kainate functional receptors (Renzel et al 2013).…”

Brain size and limits to adult neurogenesis

“…Although it has not been studied as extensively, regional restrictions likely also exist in the avian brain (Scott and Lois, 2007). Whether such spatial organization exists in the dentate SGZ of the rodent brain is under investigation (Li, et al2013; Sugiyama et al, 2013; Bekiari et al, 2014). …”