Waters, David Jack;
(1997)
Currents mediated by non-NMDA glutamate receptors in rat magnocellular basal forebrain neurones in primary culture.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Patch-clamp techniques were used to record glutamate receptor-mediated responses from magnocellular rat basal forebrain neurones maintained in dissociated culture. Both NMDA and non-NMDA receptor-mediated responses were observed and could be distinguished pharmacologically. AMPA and kainate elicited inward currents. Responses to AMPA but not to kainate showed rapid desensitization. EC50S for steady-state responses to AMPA and kainate were 2.7 and 138µM respectively. Responses were potentiated by cyclothiazide but not by Concanavalin A and were inhibited by GYKI 53655. These data indicate that non-NMDA receptor-mediated responses result predominantly from activation of an AMPA receptor. In the presence of GYKI 53655 small inward currents were observed upon kainate application. Responses decreased in amplitude during prolonged application, were insensitive to cyclothiazide and potentiated by Concanavalin A. These responses probably reflect kainate receptor activation. Steady-state current-voltage relationships were examined in nucleated patches. With 30µM spermine in the pipette mildly outwardly rectifying through linear to strongly doubly-rectifying relationships were observed, suggesting a range of calcium permeabilities. AMPA receptor calcium permeabilities were quantitated using constant field theory to interpret the effects of solution exchanges on reversal potentials in acutely dissociated neurones. Relative calcium:sodium permeability ranged from 0.26 to 3.6, median 1.27. Extracellular calcium ions also reduced current amplitude, an effect mimicked by cadmium and by cobalt ions. The effect of cadmium was dose-dependent (EC50 44µM) and voltage-sensitive. Kainate application to acutely dissociated neurones resulted in calcium current inhibition. GYKI 53655 sensitivity indicated that the probable mechanism is calcium-dependent inactivation of calcium channels following calcium influx through AMPA receptors. These data may explain the sensitivity of magnocellular cholinergic basal forebrain neurones to non-NMDA receptor agonists in vivo and are consistent with the suggestion that glutamate-induced calcium influx may contribute to selective loss of cholinergic neurones in dementia.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Currents mediated by non-NMDA glutamate receptors in rat magnocellular basal forebrain neurones in primary culture |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Biological sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10103458 |
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