Adult hippocampal neurogenesis is a unique form of neural circuit plasticity that results in the generation of new neurons in the dentate gyrus. Adult hippocampal neurogenesis originates from a population of precursor cells with glial properties. A subset of these shows morphological and antigenic. One promising approach that has recently emerged is the application of hippocampal neurogenesis to drug discovery. In this column, Carrolee Barlow, MD, PhD.
The effect was found to be prominent in the subgranular zone and evenly distributed across the distances from the granular cell layer. In Paper II we investigated whether the effect of alcohol on neurogenesis might over time affect the number and density of granule cells in the hippocampus. A morphometric method based on the principle of optical fractionator of stereology was applied on blocks of hippocampus at a standardized anatomical location. Neuronal nuclear antigen NeuN was used as a marker for mature granule cell in this study.
We found that alcohol significantly reduces the total number and density of granule cells in addition to a decrease in the volume of GCL in hippocampus. We also report that the significant difference in density was primarily due to a reduction of granule cell number. There are substantial inter-individual differences in granule cell numbers, and alcohol seemingly has a stronger impact on this than age of the subjects.
In Paper III we studied the difference in neuronal and non-neuronal cell turnover rate in control, chronic alcohol abusers and cocaine abusers. We have used a retrospective 14C birth dating procedure to estimate the average age of hippocampal cell populations and mathematical modeling to calculate the turnover rate of hippocampal cells. The turnover rate of both neuronal and non-neuronal cells in cocaine abusers were indistinguishable from control subjects, whereas we observed a lower turnover rate in alcohol abusers compared to controls.
However, this difference was not statistically significant when the results were corrected for the age of the subjects. Due to an increased loss of hippocampal neurons in alcoholics, it cannot be excluded that the true turnover rates may be lower in this group.
In conclusion, in this thesis, we have found support for impairment of neurogenesis in the hippocampus in alcoholics and that alcoholics over a lifetime have lost a substantial portion of their granule cells, which may be explained by both a reduced addition of new cells to the dentate gyrus and an increased removal of cells.
Using 14C analysis of neuronal nuclei we could not detect a significant difference in turnover of granule cells between alcoholics and controls. The team wanted to see if it could identify signs of neurogenesis in the human brain tissue given that past studies have reported mixed results about new neuron development in older human brains. To do this, the team quantified the abundance of specific proteins in hippocampal cells with marker antibody staining: There were approximately 1, neural progenitor cells per front, middle, and back of the dentate gyrus in the older adults.
However, intermediate neural progenitors did not appear to decline with age. There were thousands in each region from all the brains. Immature neurons were also present on the order of a few thousand per region of the dentate gyrus in each person, suggesting no decline in neurogenesis as people got older. Older brains also had less development of new blood vessels compared with younger brains in the anterior dentate gyrus, the team found. The front region of the dentate gyrus, Boldrini explains, has been linked to emotion and is connected to amygdala, responsible for fear and stress.
They were different cell types altogether. If neurogenesis continues in the adult human hippocampus, it is an extremely rare phenomenon.
Neurogenesis in the Adult Hippocampus
Rev Neurosci. ;18(2) Adult hippocampal neurogenesis, synaptic plasticity and memory: facts and hypotheses. Bruel-Jungerman E(1), Rampon C, . Many cellular features from this region emphasize that hippocampal neurogenesis suffers changes with normal aging and, among regulatory factors, physical. A drastic decrease in neurogenesis from adult stages toward later time points was observed; however, hippocampal neurogenesis was still.