Characterizing the expression of cholinergic neurons within the mouse dorsal subiculum
Date
2026
Authors
Girard, Daniel
Journal Title
Journal ISSN
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Publisher
University of Victoria
Abstract
Acetylcholine (ACh) is a neurotransmitter used for a variety of functions including muscle contraction and neurotransmission between neurons in the brain. Choline acetyltransferase (ChAT) is an enzyme that synthesizes ACh. Using a genetically modified mouse line (ChATcre::ChR2-YFP) allows us to visualize ChAT expression in brain regions due to the co-expression of yellow fluorescent protein (YFP). The dorsal subiculum expressed YFP fluorescence in adult mice, suggesting that this brain region is cholinergic despite previous research claiming otherwise. Using confocal microscopy, this study characterized YFP expression within the dorsal subiculum coupled with ChAT immunolabelling to examine whether this brain region contains cholinergic neurons. Brain sections from six ChATcre::ChR2-YFP mice between 59-95 days old of both sexes were examined. To validate correct YFP expression and ChAT labelling in other brain regions known to contain cholinergic neurons, we immunolabelled and quantified ChAT and YFP positive neurons in the primary visual cortex, the striatum, and medial habenula. We confirmed high YFP and ChAT co-expression from these brain regions. In the dorsal subiculum, we imaged YFP neurons, ChAT immunolabelled neurons, and NeuroTrace labelled neurons. Based on our results, the dorsal subiculum contained very few ChAT positive cholinergic neurons and is therefore non-cholinergic. Despite this, the sparse ChAT-labelling colocalized with YFP expression while the majority of YFP labelled cells did not co-express ChAT immunolabelling, suggesting that ChAT may have been present in the dorsal subiculum prior to adulthood. Future work should examine the subiculum during development to see if ChAT-labelling fully colocalizes with YFP expression.
Supervisor: Dr. Raad Nashmi