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Permanent link (DOI): https://doi.org/10.7939/R3PH54

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Modulation of Spontaneous Neural Network Bursting in Newborn Rat Brain Slices by Extracellular Calcium, Methylxanthines, and Opioids Open Access

Descriptions

Other title
Subject/Keyword
Opioids
Neonate
Early Network Oscillations (ENO)
Methylxanthines
Calcium
Calcium Imaging
Giant Depolarizing Potentials (GDP)
Caffeine
Cortex
Hippocampus
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Kantor, Chase M
Supervisor and department
Ballanyi, Klaus (Physiology)
Examining committee member and department
Karpinski, Edward (Physiology)
Nguyen, Peter (Physiology)
Cherubini, Enrico (SISSA, Neurobiology - External)
Gosgnach, Simon (Physiology)
Harvey, Steve (Physiology - Chair)
Department
Department of Physiology
Specialization

Date accepted
2012-08-27T09:44:54Z
Graduation date
2012-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Spontaneous neuronal bursting appears to be pivotal for brain maturation. This thesis studied such synchronized neural network oscillations in immature newborn rat hippocampus, cortex, and locus coeruleus. For this, horizontal brain slices were generated for (simultaneous) suction electrode recording of extracellular population bursting in these structures and monitoring their electrical activity indirectly at cellular resolution via imaging of associated cytosolic Ca2+ rises. In a first project, it was found that all rhythms were robust and stable for several hours in superfusate with close-to-physiological content of the neuroactive cations Ca2+ (1 mM) and K+ (3-4 mM) and were depressed by superfusate with elevated (1.5-3 mM) Ca2+ content and this inhibition was countered by raising K+ to 5-7 mM (‘Ca2+/K+ antagonism’). This thesis studied how the above hippocampal and cortical rhythms are affected by two classes of drugs that are frequently administered to (preterm) human infants: (i) the methylxantines caffeine and theophylline which are the gold standard for treatment of apneas of prematurity, but can evoke seizures, and (ii) opioids that are used for analgesia, but can depress breathing by inhibiting medullary respiratory network bursting. It was found that submillimolar bath-applied methylxanthine tended to increase the rate and/or amplitude of hippocampal and cortical bursts. At low millimolar doses, they suppressed normal rhythm in both areas and evoked large amplitude rhythmic seizure-like discharges. Similar seizure-like discharges were evoked in the hippocampus, but not cortex, by bath-application of 1-10 µM of the µ-opioid receptor agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO), which blocked locus coeruleus rhythm. In summary, the findings indicate that hippocampal, cortical and locus coeruleus networks in newborn rat horizontal slices show robust bursting in solution with close-to-physiological extracellular Ca2+ and K+ levels. Methylxanthines cause seizure-like discharges at doses that are likely higher than in extracellular brain tissue in vivo during clinical application. Opioids exert their typical inhibitory action on locus coeruleus neurons; however, they do not suppress bursting in cortex and hippocampus, but rather evoke hyperexcitability in the latter area. Potential mechanisms of methylxantine- and opioid-evoked perturbation of network oscillations are discussed including potential consequences for maturation of these neural circuits.
Language
English
DOI
doi:10.7939/R3PH54
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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