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Title: A patch-clamp study of glutamate receptor channels and glutamate uptake in rat cerebellar neurones and glia
Author: Wyllie, David James Angus
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1992
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Whole-cell and outside-out configurations of the patch-clamp recording technique have been used to investigate the properties of non-NMDA glutamate receptor-channels present in granule neurones and macroglia cells in rat cerebellar cultures. Of the various types of glial cell present in such cultures only type-2 astrocytes and oligodendrocyte/type-2 astrocyte (O-2A) progenitor cells possessed 'fast' glutamate non-NMDA receptor-channels, whereas type-1-like astrocytes and oligodendrocytes lacked receptor channels. No evidence was found for the presence of NMDA channels in any of the glial cell types. In addition, type-1-like astrocytes were unique in possessing a detectable electrogenic uptake carrier for glutamate. Further investigations revealed that "glial" and "neuronal" type non-NMDA receptors were similar in many of their pharmacological properties. However, in one clear respect they differed; analysis of single channels in outside-out patches isolated from type-2 astrocytes and granule cells indicated that in addition to opening to conductance levels of between 10 and 30pS, the non-NMDA channels in these cells also opened to 40 and 50pS conductance levels (~20% of all activations). There was no evidence in granule cells that non-NMDA channels could give rise to large conductance (40/50pS) openings. A detailed investigation has been made of non-NMDA receptor-channels present in excised membrane patches of cerebellar granule neurones. Application of non-NMDA receptor agonists to membrane patches evoked two types of response, which were termed 'high' and 'low' conductance type responses. In high conductance patches glutamate, AMPA and kainate each opened resolvable single channels that had conductances of approximately 10, 20 and 30pS. Kainate responses in low conductance patches were characterized by a small noise increase in the current trace and a small DC shift, whereas AMPA opened resolvable channels in such patches, but such channels had conductances of mainly 5pS. In addition to investigating the conductance levels of non-NMDA receptor-channels, a preliminary kinetic analysis of these channels was undertaken. It is proposed from the experiments on high and low conductance patches that cerebellar granule neurones possess more than one type of non-NMDA channel.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available