Number Of Granule Cells In Dentate Gyrus Research Articles

Pattern separation in the dentate gyrus: a role for the CA3 backprojection.

Many theories of hippocampal function assume that area CA3 of hippocampus is capable of performing rapid pattern storage, as well as pattern completion when a partial version of a familiar pattern is presented, and that the dentate gyrus (DG) is a preprocessor that performs pattern separation, facilitating storage and recall in CA3. The latter assumption derives partly from the anatomical and physiological properties of DG. However, the major output of DG is from a large number of DG granule cells to a smaller number of CA3 pyramidal cells, which potentially negates the pattern separation performed in the DG. Here, we consider a simple CA3 network model, and consider how it might interact with a previously developed computational model of the DG. The resulting "standard" DG-CA3 model performs pattern storage and completion well, given a small set of sparse, randomly derived patterns representing entorhinal input to the DG and CA3. However, under many circumstances, the pattern separation achieved in the DG is not as robust in CA3, resulting in a low storage capacity for CA3, compared to previous mathematical estimates of the storage capacity for an autoassociative network of this size. We also examine an often-overlooked aspect of hippocampal anatomy that might increase functionality in the combined DG-CA3 model. Specifically, axon collaterals of CA3 pyramidal cells project "back" to the DG ("backprojections"), exerting inhibitory effects on granule cells that could potentially ensure that different subpopulations of granule cells are recruited to respond to similar patterns. In the model, addition of such backprojections improves both pattern separation and storage capacity. We also show that the DG-CA3 model with backprojections provides a better fit to empirical data than a model without backprojections. Therefore, we hypothesize that CA3 backprojections might play an important role in hippocampal function.

Increased adult neurogenesis in the subventricular zone in a rat model of sepsis

Neurogenesis occurs in the adult brain throughout the lives of all mammals. The dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ) of the lateral ventricles have been established as the primary sites of adult neurogenesis, and recent studies have shown that inflammation has a modulating effect on adult neurogenesis. However, only limited studies have investigated how neurogenesis is affected during sepsis and sepsis-associated encephalopathy. Therefore, we investigated adult neurogenesis in the cecal ligation and puncture (CLP) model of sepsis using a cell proliferation marker, 5-bromo-2′-deoxyuridine (BrdU). Twenty-four rats were placed into the following three groups: an un-operated control group, a sham-operated group that underwent exactly the same procedures except for CLP, and a CLP group that survived surgical procedures and developed signs of sepsis. Rats were monitored for twenty-four hours before they were euthanized and their brains were harvested. Significantly higher numbers of BrdU-immunoreactive cells were observed in the SVZ of the lateral ventricles in the CLP group as compared with both control groups, while no significant difference was found in the number of DG granule cells between the three groups. The majority of BrdU-positive cells in the SVZ co-expressed the neuronal marker doublecortin but not the astrocytic marker glial fibrillary acidic protein. Taken together, our results suggest that sepsis induced by CLP in rats increases region-specific cellular regeneration, in a possible attempt to compensate for the devastating effect of sepsis and sepsis-associated encephalopathy on the brain.

Postnatal neurogenesis in the hippocampal dentate gyrus and subventricular zone of the Göttingen minipig

Postnatal neurogenesis is currently viewed as important for neuroplasticity and brain repair. We are, therefore, interested in animal models for neuroimaging of postnatal neurogenesis. A recent stereological study found an age-dependent increase in the number of neurons and glial cells in the neocortex of Göttingen minipigs, suggesting that this species may be characterized by a prolonged postnatal neurogenesis. Since there is no direct evidence on this issue, the goal of our study was to quantify cell proliferation in the two major neurogenic regions of the postnatal brain – the subventricular zone of the lateral ventricle (SVZ) and the hippocampal dentate gyrus (DG) – at two separate points during the lifespan of the minipig. Göttingen minipigs aged 6–7 and 32 weeks were injected with bromodeoxyuridine (BrdU), a marker of cycling cells, and killed after 2 h. We found BrdU-positive cells numbering 165,000 in the SVZ and 35,000 in the DG at 6–7 weeks and 66,000 in the SVZ and 19,000 in the DG at 32 weeks-of-age. Stereology showed a 60% increase in the total number of DG granule cells between 6–7 and 32 weeks-of-age. Our findings show a continued postnatal neurogenesis in the major neurogenic regions of Göttingen minipigs, thereby providing a potential animal model for studies aimed at examining ongoing neurogenesis in the living brain with molecular neuroimaging technology.

Royal Jelly Facilitates Restoration of the Cognitive Ability in Trimethyltin‐Intoxicated Mice

Trimethyltin (TMT) is a toxic organotin compound that induces acute neuronal death selectively in the hippocampal dentate gyrus (DG) followed by cognition impairment; however the TMT-injured hippocampal DG itself is reported to regenerate the neuronal cell layer through rapid enhancement of neurogenesis. Neural stem/progenitor cells (NS/NPCs) are present in the adult hippocampal DG, and generate neurons that can function for the cognition ability. Therefore, we investigated whether royal jelly (RJ) stimulates the regenerating processes of the TMT-injured hippocampal DG, and found that orally administered RJ significantly increased the number of DG granule cells and simultaneously improved the cognitive impairment. Furthermore, we have already shown that RJ facilitates neurogenesis of cultured NS/NPCs. These present results, taken together with previous observations, suggest that the orally administered RJ may be a promising avenue for ameliorating neuronal function by regenerating hippocampal granule cells that function in the cognition process.