Intracellular calcium has been widely demonstrated as an important part of intracellular signalling pathways. Entry of calcium in cells has been shown to trigger a variety of processes such as contraction in smooth and skeletal muscle, release of neurotransmitter in neurons and activation of modifying proteins in most cells, which in turn will activate or deactivate other processes. For these reasons, calcium permeation through any ion-channel type, whether ligand or voltage-gated, expressed on the surface of a cell, might potentially influence the intracellular activities or status of that cell. Calcium permeation in muscle nicotinic acetylcholine receptors has long been shown unequivocally. Calcium permeation through neuronal nAChR's has also been shown, but these experiments were done on preparations of neurons. Typically, neurons might express two or three subunits of the same type. The lack of knowledge on the assembly of subunits into receptors and the possibility that subunits might be permutable in a receptor make the exact subunit composition of the receptors unknown. To test the hypothesis that calcium is a permeant ion of the alpha 4beta2 subtype neuronal nicotinic acetylcholine receptor (nAChR), I performed single-channel patch-clamp experiments on micro-injected Xenopus oocytes expressing alpha4beta2 neuronal nAChR. When recording from single cell receptors in increasing concentration of extracellular Ca2+ I found that the amplitude of the single-channel current decreased with each increment in concentration. The behaviour of the resulting current-voltage relationships is described as a direct influence of calcium permeation on single-channel current amplitude. Analysis with a theoretical model describing permeation at the single-channel level supported this conclusion.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.21618 |
| Date | January 1998 |
| Creators | Paquet, Michel. |
| Contributors | Cooper, E. J. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001650637, proquestno: MQ50850, Theses scanned by UMI/ProQuest. |
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