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Reference: Pollard, Marie., (2001). Differential involvement of glutamate receptors in neuronal responses of the cerebral cortex. DPhil. University of Oxford.Citable link to this page:

 

Differential involvement of glutamate receptors in neuronal responses of the cerebral cortex

Abstract: I studied how glutamate receptor-mediated responses, spatial arrangements, intrinsicproperties and molecular specificity of cells serve cortical functions. I tested whether twosomatosensory submodalities in the primary somatosensory (SI) cortex can be distinguished byglutamate receptor involvement in vivo. Low-threshold responses evoked by innocuous stimulihad a short-duration and long-duration component. The short-duration responses were mostlymediated by AMPA/kainate receptors and the long-duration responses involved the additionalrecruitment of NMDA receptors. High-threshold responses evoked by noxious stimuli wereunimodal and mediated by both AMPA/kainate and NMDA receptors throughout the entireresponse. During noxious stimulus trials, an increase in baseline activity in SI cortical cells wasobserved. I attribute the changes in baseline activity to cells in the medial thalamic nuclei, whichproject to the SI cortex and are involved in the affective-motivational aspects of nociceptivesignalling.To gain insight into the influence of synaptic organisation of a well-defined cortical area,I studied in vitro whether the intrinsic properties of two anatomically well-defined nonpyramidalcells in the hippocampus can provide clues into the modulation of neuronal signalling. During adepolarising current pulse, O-LM and O-Bi cells were distinguished by their accommodation ofaction potentials depending on the early or late part of the response. Also, during ahyperpolarising current pulse, O-LM cells displayed a prominent voltage 'sag' as compared toO-Bi cells. Both cell types contain somatostatin and I showed that O-LM cells express themetabotropic glutamate receptor type 1α. Although O-LM and O-Bi cells have a similarsomatodendritic position their different axonal arbours imply that they are involved in thefeedback modulation of the entorhinal and CA3 glutamatergic influences, respectively. I alsofound that contrary to previous reports not only somatostatin but also vasoactive intestinalpolypeptide containing cells express mGluR1α, which might facilitate their oscillatoryresponses.To relate the action potential discharge of specific cortical cell classes to behaviourallyrelevant network activity, I also sought to identify hippocampal cells following in vivorecording. Novel information was provided for both the temporal and anatomical properties ofcells not recorded previously. In particular, a putative interneuron targeting nonpyramidal celland backprojection cell was recorded in relation to theta field events. A novel nonpyramidalprojection cell was recorded in relation to sharp wave field events. A remarkable specificity wasfound in the dendritic and axonal patterns of these cells.The results show that distinct types of glutamate receptors are differentially involved incortical function. The intrinsic properties and expression of mGluR1α in particular is highlyspecific in distinct nonpyramidal cell classes.

Type of Award:DPhil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:The digital copy of this thesis has been made available thanks to the generosity of Dr Leonard Polonsky

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Somogyi, PeterMore by this contributor

RoleSupervisor

 

Prof. Peter SomogyiMore by this contributor

RoleSupervisor

 Bibliographic Details

Issue Date: 2001Identifiers

Urn: uuid:f6c716f7-021d-4d73-8108-493fdd51e8ae

Source identifier: 602819910 Item Description

Type: Thesis;

Language: eng Subjects: Monosodium glutamate Receptors Cerebral cortex Tiny URL: td:602819910

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Author: Pollard, Marie. - institutionUniversity of Oxford facultyMedical Sciences Division - - - - Contributors Somogyi, Peter More by th

Source: https://ora.ox.ac.uk/objects/uuid:f6c716f7-021d-4d73-8108-493fdd51e8ae



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