Survey of Brain Variations of Young Adult and Aged B2 (-/-) Knockout Mice
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Neuronal nicotinic acetylcholine receptors (nAChRs) are pentameric, ligand-gated ion channels whose activation is triggered by the neurotransmitter acetylcholine and by the exogenous compound, nicotine. In previous studies, disruptions in high affinity nAChR function have been shown to contribute to neuronal dysfunction as observed in Alzheimer’s disease (AD), Parkinson’s disease (PD), Lewy body dementia, autism, epilepsy, and schizophrenia. To study the effect of nAChRs, knockout mice, or mice genetically altered to lack certain subunits of their nAChRs, have been created. β2 (-/-) knockout mice lack the β2 subunit of their nicotinic acetylcholine receptors. These β2 (-/-) knockout mice have been shown to have a shorter lifespan, altered brain development and altered CNS function similar to changes seen in human ageing, making them a useful animal model for human dementia and neurodegeneration. It has been hypothesized that the β2 subunit has neuroprotective properties with respect to the neurons that express nicotinic acetylcholine receptors. The purpose of this study is to compare the volumes and cell densities of the olfactory bulb and the hippocampus in young adult (2-3 month old) and aged (18 month old) male β2 (-/-) knockout mice and age-matched wild type (+/+) mice. Both the olfactory bulb and hippocampus exhibit adult neurogenesis and the hippocampus is an important center for spatial learning and memory. We hypothesized that mice lacking the β2 subunit of their nAChRs, have excessive cell loss and therefore decreased brain area and that this effect would be pronounced in older β2 (-/-) knockout mice compared to younger mice. Currently, young adult mice (2-3 month old), have been evaluated, and no significant statistical difference in the olfactory bulb volume or hippocampus volume in β2(-/-) knockout mice compared to age-matched control mice has been observed. The olfactory bulb granular cell layer density of 2-3 month old mice also showed no significant difference compared to age-matched control mice. In aged mice (18 months old), hippocampus volumes and olfactory bulb volumes were measured and found to be the same as observed in the age-matched wild type group. In the future, cell densities of hippocampus in young adult mice and cell densities of olfactory bulb and hippocampus of aged mice, should be studied.
Kuban, J Katherine (2008). Survey of Brain Variations of Young Adult and Aged B2 (-/-) Knockout Mice. Available electronically from