Adult Dentate Gyrus (adult + dentate_gyrus)

Distribution by Scientific Domains


Selected Abstracts


The corticoid environment: a determining factor for neural progenitors' survival in the adult hippocampus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004
Edmund Y. H. Wong
New neurons continue to be generated in the adult dentate gyrus of the hippocampus. Corticosterone (CORT), a steroid secreted by the adrenal glands, had been shown to regulate progenitor proliferation. High levels of CORT suppress proliferation while low levels of the steroid stimulate it. Here we present an investigation into the regulation of survival by corticoids, with emphasis on the differential effects of the pre-mitotic and post-mitotic corticoid environments. Post-mitotic adrenalectomy increased subsequent survival of progenitors at 28 days, while additional CORT administered during the post-mitotic period decreased survival. In contrast, a corticoid-free environment prior to progenitor division resulted in a reduced survival rate of new cells and, similarly, high levels of CORT before proliferation reduced subsequent survival. In addition, phased treatment with CORT during a 27-day post-mitotic interval showed that newly formed cells lose their sensitivity to administered CORT after about 18 days. These results are the first to show that the corticoid environment both before and after cell division regulates survival. [source]


Efficacy of doublecortin as a marker to analyse the absolute number anddendritic growth of newly generated neurons in the adult dentate gyrus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004
Muddanna S. Rao
Abstract Doublecortin (DCX), a microtubule-associated phosphoprotein, has been recently utilized as a marker of newly born neurons in the adult dentate gyrus (DG). Nonetheless, it is unknown whether DCX exclusively labels newly formed neurons, as certain granule cells with the phenotype of differentiated neurons express DCX. We addressed the authenticity of DCX as a marker of new neurons in the adult DG by quantifying cells that are positive for 5,-bromodeoxyuridine (BrdU), DCX and both BrdU and DCX in hippocampal tissues of adult rats treated with daily injections of BrdU for 12 consecutive days. We provide new evidence that neurons visualized with DCX immunostaining in the adult rat DG are new neurons that are predominantly born during the 12 days before euthanasia. This is confirmed by the robust expression of BrdU in 90% of DCX-positive neurons in the DG of animals injected with BrdU for 12 days. Furthermore, DCX expression is specific to newly generated healthy neurons, as virtually all DCX-positive cells express early neuronal antigens but lack antigens specific to glia, undifferentiated cells or apoptotic cells. As DCX expression is also robust in the dendrites, DCX immunocytochemistry of thicker sections facilitates quantification of the dendritic growth in newly born neurons. Thus, both absolute number and dendritic growth of new neurons that are generated in the adult DG over a 12-day period can be quantified reliably with DCX immunostaining. This could be particularly useful for analysing changes in dentate neurogenesis in human hippocampal tissues as a function of ageing or neurodegenerative diseases. [source]


Serotonin mediates oestrogen stimulation of cell proliferation in the adult dentate gyrus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001
Mounira Banasr
Abstract Characterizing the mechanisms by which endogenous factors stimulate neurogenesis is of special interest in view of the possible implication of newly generated cells in hippocampal functions or disorders. The aim of this study was to determine whether serotonin (5-HT) and oestradiol (E2) act through a common pathway to increase cell proliferation in the adult dentate gyrus (DG). We also investigated the effects of long-lasting changes in oestrogen levels on cell proliferation. Combining ovariectomy with inhibition of 5-HT synthesis using p -chlorophenylalanine (PCPA) treatment produced approximately the same decreases in the number of bromodeoxyuridine (BrdU) and PSA-NCAM immunolabelled cells in the subgranular layer as ovariectomy alone. Administration of 5-hydroxytryptophan (5-HTP) restored cell proliferation primarily decreased by ovariectomy, whereas oestradiol was unable to reverse this change in ovariectomized rats treated with PCPA. These findings demonstrate that 5-HT mediates oestrogen stimulation of cell proliferation in adult dentate gyrus. However, increase in ovarian hormones during pregnancy has no effect on dentate cell proliferation. This finding suggests that concomitant changes in other factors, such as glucocorticoids, may counterbalance the positive regulation of cell proliferation by 5-HT and oestradiol. Finally, oestrogen may regulate structural plasticity by stimulating PSA-NCAM expression independently of neurogenesis, as shown for instance by the increases in the number of PSA-NCAM labelled cells in pregnants. As 5-HT and oestrogen are involved in mood disorders, our data suggest that the positive regulation of cell proliferation and neuroplasticity by these two factors may contribute to restore hippocampal connectivity in depressive patients. [source]


Role of the cholinergic system in regulating survival of newborn neurons in the adult mouse dentate gyrus and olfactory bulb

GENES TO CELLS, Issue 10 2006
Naoko Kaneko
Neurogenesis in the subgranular zone of the hippocampal dentate gyrus and olfactory bulbs continues into adulthood and has been implicated in the cognitive function of the adult brain. The basal forebrain cholinergic system has been suggested to play a role in regulating neurogenesis as well as learning and memory in these regions. Herein, we report that highly polysialylated neural cell adhesion molecule (PSA-NCAM)-positive immature cells as well as neuronal nuclei (NeuN)-positive mature neurons in the dentate gyrus and olfactory bulb express multiple acetylcholine receptor subunits and make contact with cholinergic fibers. To examine the function of acetylcholine in neurogenesis, we used donepezil (Aricept), a potent and selective acetylcholinesterase inhibitor that improves cognitive impairment in Alzheimer's disease. Intraperitoneal administrations of donepezil significantly enhanced the survival of newborn neurons, but not proliferation of neural progenitor cells in the subgranular zone or the subventricular zone of normal mice. Moreover, donepezil treatment reversed the chronic stress-induced decrease in neurogenesis. Taken together, these results suggest that activation of the cholinergic system promotes survival of newborn neurons in the adult dentate gyrus and olfactory bulb under both normal and stressed conditions. [source]


The effects of exercise and stress on the survival and maturation of adult-generated granule cells,

HIPPOCAMPUS, Issue 10 2009
Jason S. Snyder
Abstract Stress strongly inhibits proliferation of granule cell precursors in the adult dentate gyrus, whereas voluntary running has the opposite effect. Few studies, however, have examined the possible effects of these environmental manipulations on the maturation and survival of young granule cells. We examined the number of surviving granule cells and the proportion of young neurons that were functionally mature, as defined by seizure-induced immediate-early gene (IEG) expression, in 14- and 21-day-old granule cells in mice that were given access to a running wheel, restrained daily for 2 h, or given no treatment during this period. Treatments began 2 days after BrdU injection, to isolate effects on survival from those on cell proliferation. We found a large increase in granule cell survival in running mice when compared with controls at both time points. In addition, running increased the proportion of granule cells expressing the IEG Arc in response to seizures, suggesting that it speeds incorporation into circuits, i.e., functional maturation. Stressed mice showed no change in Arc expression, compared with control animals, but, surprisingly, showed a transient increase in survival of 14-day-old granule cells, which was gone 7 days later. Examination of cell proliferation, using the endogenous mitotic marker PCNA showed an increase in cell proliferation after 12 days of running but not after 19 days of running. The number of proliferating cells was unchanged 24 h after the 12th or 19th episode of daily restraint stress. These findings demonstrate that running has strong effects on survival and maturation of young granule cells as well as their birth and that stress can have positive but short-lived effects on granule cell survival. Published 2009 Wiley-Liss, Inc. [source]


A Distinctive layering pattern of mouse dentate granule cells is generated by developmental and adult neurogenesis

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 22 2010
Emily A. Mathews
Abstract New neurons are continuously added throughout life to the dentate gyrus of the mammalian hippocampus. During embryonic and early postnatal development, the dentate gyrus is formed in an outside-in layering pattern that may extend through adulthood. In this work, we sought to quantify systematically the relative position of dentate granule cells generated at different ages. We used 5,-bromo-2,-deoxyuridine (BrdU) and retroviral methodologies to birth date cells born in the embryonic, early postnatal, and adult hippocampus and assessed their final position in the adult mouse granule cell layer. We also quantified both developmental and adult-born cohorts of neural progenitor cells that contribute to the pool of adult progenitor cells. Our data confirm that the outside-in layering of the dentate gyrus continues through adulthood and that early-born cells constitute most of the adult dentate gyrus. We also found that substantial numbers of the dividing cells in the adult dentate gyrus were derived from early-dividing cells and retained BrdU, suggesting that a subpopulation of hippocampal progenitors divides infrequently from early development onward. J. Comp. Neurol. 518:4479,4490, 2010. © 2010 Wiley-Liss, Inc. [source]