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Calcium Imaging and Field Potential Analysis of Autocrine Neuromodulation in the Locus Coeruleus of Newborn Rat Brain Slices
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- Author / Creator
- Waselenchuk, Quinn
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The locus coeruleus (LC) is a small brainstem nucleus that controls diverse behaviours and brain functions via release of noradrenaline (NA) in the neonatal time period. There is increasing evidence of complexity in this neuron-astrocyte ‘neural’ network that remains mostly unexplored in neonates. Our group has established that in acutely isolated horizontal slices from newborn rat brains, the LC produces a local field potential (LFP) that can be recorded using suction electrodes, and that activity in individual neurons and astrocytes can be indirectly measured using cytosolic Ca2+ (Cai) imaging. The overall aim of this thesis was to perform experiments in vitro that exemplify the complexity of this network thus establishing a basis for future studies, particularly involving neuron-astrocyte interactions.
First, immunohistochemistry on chemically fixed slices found a unique distribution of LC neurons and astrocytes such that density of astrocyte somata was lower within the LC neuron soma area, whereas it was higher in the surroundings. A similar anatomical result was then found in acutely isolated living slices bulk loaded with the Ca2+ sensitive fluorescent dye Fluo-4. Next, combined Cai imaging and LFP recording during bath application of NA to mimic autocrine activity consolidated that NA depressed activity in neurons while it evoked an excitatory concentric Cai wave in astrocytes. Comparison with the effects of two other modulators, adenosine triphosphate (ATP) and trans-1-amino-1,3-dicarboxycyclopentane (t-ACPD), determined that ATP also evoked concentric astrocyte waves while t-ACPD did not. Additionally, different subpopulations of neurons and astrocytes responded to one of or a combination of these three modulators.
Together, this is the first study to show that astrocytes in any brain region propagate waves that travel in a concentric fashion and contributes to evidence of modular organization in the neonatal LC. This establishes that the neonatal LC neural network has a complex organization and highlights the possible role of neuron-astrocyte interactions, providing a foundation for future studies on neuronal and glial activity in this nucleus.
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- Subjects / Keywords
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- Graduation date
- Fall 2022
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.