Synaptogenesis and spinogenesis of adult hippocampal neurogenesis in laboratory long-evans rat exposed to enriched environment
Date
2017
Authors
Uzokwe, Chioma Blessing
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Abstract
This research studied adult hippocampal neurogenesis in the dentate gyrus of the hippocampus of the Long-Evans rat. Eighteen male Long-Evans rats were exposed to complex enriched environment, the running wheel environment for exercise as single influencing factor and the standard laboratory environment for 28 days. Thereafter the rats were transcardially perfused with 0.9 normal saline followed by 4% paraformaldehyde. The brains were removed and frozen sagittal sections cut at 50 μm. Brain sections were stained with Cresyl violet for cytoarchitecture. Immunohistochemistry and immunofluorescence techniques were employed for the immature neurons with defined processes using the marker doublecortin (DCX), neuronal proliferation marker Ki-67, the synapse marker, synaptophysin and the dendritic spine marker, synaptobrevin. Giemsa staining was used to identify pyknotic neurons followed by counts for DCX, Ki-67, pyknotic positive cells, and volume density of the dentate gyrus. Results indicated a statistically significant increase in brain weight (p=0.5) for the complex enriched group when compared to the running group and control. The typical cytoarchitecture of the hippocampus in rodents was observed with more densely packed granule cell layer in the dorsal limb of the dentate gyrus compared to the ventral limb especially in the enriched group. The Ki-67 immunopositive cell number between groups showed a variable difference with a three-fold increase each between the standard control and exercise, and between the exercise and enriched but a six-fold increase between the standard control and the complex enriched groups. Comparing the DCX immunopositive results, we observed also that the neuronal numbers, structure, dendritic patterns as well as the neuronal arrangement on the dorsal and ventral limbs of the dentate gyrus varied significantly among groups. The apoptotic cell numberusing pyknotic cells, showed the standard control group to have the highest number of cells compared to the exercise versus the enriched group; noting a five-fold difference between the standard control and exercise, a twenty seven-fold difference between the standard control versus enriched and a twenty one-fold difference between
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the exercise and complex enriched group. The volumetric analysis showed a 15-fold difference between the standard control and exercise groups, a five-fold difference between the exercise and complex enriched and a nineteen-fold difference between the standard control and complex enriched groups. However, no statistical significant difference was found in the volumetric analysis of the dentate gyrus between the groups.
Description
A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of;
Masters of Science in Medicine (Anatomical Sciences)
School of Anatomical Sciences,
Faculty of Health Sciences,
University of the Witwatersrand,
Johannesburg.
2017.