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Characterization of glutamate-gated chloride channels in the pharynx of wild-type and mutant Caenorhabditis elegans delineates the role of the subunit GluCl-alpha 2 in the function of the native receptor

Record type: Article

Glutamate-gated chloride (GluCl) channels are the site of action of the anthelmintic ivermectin. Previously, the Xenopus laevis oocyte expression system has been used to characterize GluCl channels cloned from Caenorhabditis elegans. However, information on the native, pharmacologically relevant receptors is lacking. Here, we have used a quantitative pharmacological approach and intracellular recording techniques of C. elegans pharynx to characterize them. The glutamate response was a rapidly desensitizing, reversible, chloride-dependent depolarization (EC50 = 166 µM), only weakly antagonized by picrotoxin. The order of potency of agonists was ibotenate > L-glutamate > kainate = quisqualate. Ivermectin potently and irreversibly depolarized the muscle (EC50 = 2.7 nM). No further depolarization was seen with coapplication of maximal glutamate during the maximal ivermectin response, indicating that ivermectin depolarizes the muscle by the same ionic mechanism as glutamate (i.e., chloride). The potency of ivermectin on the pharynx was greater than at any of the GluCl subunits expressed in X. laevis oocytes. This effect of ivermectin was abolished in the mutant avr-15, which lacks a functional GluCl-alpha 2 subunit. However, a chloride-dependent, nondesensitizing response to glutamate persisted. Therefore, the GluCl-alpha 2 subunit confers ivermectin sensitivity and a high-affinity desensitizing glutamate response on the native pharyngeal GluCl receptor.

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Citation

Pemberton, D.J., Franks, C.J., Walker, R.J. and Holden-Dye, L. (2001) Characterization of glutamate-gated chloride channels in the pharynx of wild-type and mutant Caenorhabditis elegans delineates the role of the subunit GluCl-alpha 2 in the function of the native receptor Molecular Pharmacology, 59, (5), pp. 1037-1043.

More information

Published date: 1 May 2001

Identifiers

Local EPrints ID: 56754
URI: http://eprints.soton.ac.uk/id/eprint/56754
ISSN: 0026-895X
PURE UUID: 47f1f92e-69ec-4649-acaf-2e73e6a9c9fe
ORCID for C.J. Franks: ORCID iD orcid.org/0000-0002-5412-7037

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Date deposited: 08 Aug 2008
Last modified: 17 Jul 2017 14:30

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Contributors

Author: D.J. Pemberton
Author: C.J. Franks ORCID iD
Author: R.J. Walker
Author: L. Holden-Dye

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