Spreading Depolarization Evoked by Oxygen-Glucose Deprivation or by Temperature Change in Frog and Rat Brain Slices
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Authors
Donovan, Victoria
Date
Type
thesis
Language
eng
Keyword
Spreading Depolarization , Ischemia , Rana pipiens , Light Transmittance Imaging , Oxygen Glucose Deprivation , Higher Brain Shutdown
Alternative Title
Abstract
As a result of anoxia or abrupt change in temperature spreading depolarizations (SD)
occur in the grey matter of the higher brain, promoting neuronal injury. SD in mammals and
insects induces a sudden shutdown of the central nervous system (CNS) gray matter, but it is
unclear if SD is generated in the cerebral cortex (CC) of lower vertebrates. In this study, the
effects of oxygen glucose deprivation (OGD, which simulates ischemia) or abrupt temperature
change was studied on live coronal brain slices from Northern Leopard frog (Rana pipiens) and
Sprague Dawley rat (Rattus norvegicus) brain slices to compare SD susceptibility. We
hypothesized that this cold-blooded vertebrate generates SD, reflecting the need for a shutdown
capability, but that the frog brain is less susceptible to anoxia or temperature change because of
its variable environment. We used light transmittance imaging (LT) during exposure to various
solutions/temperatures to examine whether frog CC can generate SD and if so, its propensity to
initiate and propagate compared to the rat. The frog CC generated delayed OGD-SD at 12±2.6
min (mean ± SE) at 35oC (n=8) compared to rat slices at 1.6±0.34 min at 35oC (n=4). The frog
CC generated ouabain-SD at 5.6±0.3 min at 35oC (n=12) compared to 4.8 min on average in rat
neocortex as shown previously in our lab. At 26oC, frog slices generated SD induced by 100 M
ouabain (a Na+/K+pump inhibitor) at 9.3±0.5 min (n=12) compared to rat slices at 6.6±0.2 min
(n=10). Unlike in rat, SD was not evoked in frog CC by elevating bath [K+]o to 26 mM at any of
the tested temperatures. A 35 to 40⁰C ramp generated SD at 10.8±1.1 min (n=6) in frogs and
5.5±0.5 min (n=16) in rats. A 35 to 4.7⁰C ramp generated SD in the rat at 2.5±0.6 min (n=8) but
did not elicit SD in the frog. Our findings show that the capacity to generate SD in the cerebral
cortex evolved early in vertebrate evolution. However, the frog CC is less sensitive to SD
shutdown evoked by simulated ischemia or by sudden temperature change. This appears
appropriate to the amphibian environment where oxygen content of the water and ambient
temperature vary considerably.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.