Novel modes of communication between neuronal activity and microglial process dynamics
department or school: Medicine, Faculty of
data provider: DSpace
degree campus: UBCV
creator: Dissing-Olesen, Lasse
issued: 2015-04-28T17:29:52Z
issued: 2015
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Microglia are morphologically dynamic cells that survey neuronal dendrites and rapidly respond to ATP. However, the role of ATP in mediating neuron-microglia communication remains to be determined. We therefore investigated the question whether high neuronal activity would evoke ATP release and thereby trigger a change in microglial process dynamics. To address this we used acute hippocampal brain slices and two-photon laser scanning microscopy and we developed a novel method for fixation and immunolabeling of microglia processes. We discovered that multiple brief applications of NMDA triggered a transient outgrowth of microglia processes similar to application of ATP. The outgrowth was reversible and repeatable, indicating that it was not due to excitotoxic damage. ATP release, secondary to NMDAR activation, was the key mediator as blocking purinergic receptors abolished outgrowth. Hemichannel opening is a well-defined mechanism for ATP release, but outgrowth still occurred in the absence of the hemichannel protein pannexin 1 and in the presence of the hemichannel blocker carbenoxolone. Utilizing whole cell patch clamping we demonstrated that activation of dendritic NMDAR on single neurons was sufficient to trigger microglia process outgrowth. These results suggest that dendritic neuronal NMDAR activation triggers ATP release via a hemichannel-independent mechanism. It is well established that high neuronal activity leads to a reduction in extracellular Ca²+ which causes opening of astrocytic Cx43 hemichannels and subsequent ATP release. We therefore investigated whether hemichannel opening could trigger a change in microglial process dynamics. Indeed, removal of extracellular Ca²+ triggered a microglial response, which we refer to as microglial process focalization because it was distinctively different from the NMDA-evoked process outgrowth. This focalization was also mediated by ATP as it was blocked by selective blockade of microglial purinergic receptors and w…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/52982
note: NOVEL MODES OF COMMUNICATION BETWEEN NEURONAL ACTIVITY AND MICROGLIAL PROCESS DYNAMICS by Lasse Dissing-Olesen M.Sc., University of Southern Denmark, 2009 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Neuroscience) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2015 © Lasse Dissing-Olesen, 2015 ii Abstract Microglia are morphologically dynamic cells that survey neuronal dendrites and rapidly respond to ATP. However, the role of ATP in mediating neuron-microglia communication remains to be determined. We therefore investigated the question whether high neuronal activity would evoke ATP release and thereby trigger a change in microglial process dynamics. To address this we used acute hippocampal brain slices and two-photon laser scanning microscopy and we developed a novel method for fixation and immunolabeling of microglia processes. We discovered that multiple brief applications of NMDA triggered a transient outgrowth of microglia processes similar to application of ATP. The outgrowth was reversible and repeatable, indicating that it was not due to excitotoxic damage. ATP release, secondary to NMDAR activation, was the key mediator as blocking purinergic receptors abolished outgrowth. Hemichannel opening is a well-defined mechanism for ATP release, but outgrowth still occurred in the absence of the hemichannel protein pannexin 1 and in the presence of the hemichannel blocker carbenoxolone. Utilizing whole cell patch clamping we demonstrated that activation of dendritic NMDAR on single neurons was sufficient to trigger microglia process outgrowth. These results suggest that dendritic neuronal NMDAR activation triggers ATP release via a hemichannel-independent mechanism. It is well established that high neuronal activity leads to a reduction in extracellular Ca2+ which causes opening of astrocytic Cx43 hemichannels and subsequent ATP release. We therefore …
has type: Thesis/Dissertation
date issued: 2015-09
is shown at: 10.14288/1.0167700
language: eng
degree discipline: Neuroscience
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivs 2.5 Canada
rights URI: http://creativecommons.org/licenses/by-nc-nd/2.5/ca/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/52982