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Nonselective cation conductance activated by muscarinic and purinergic receptors in rat spiral ganglion neurons

Nonselective cation conductance activated by muscarinic and purinergic receptors in rat spiral... Abstract The present study characterizes the ionic conductances activated by acetylcholine (ACh) and ATP, two candidate neuromodulators, in isolated spiral ganglion neurons (SGNs). Brief application (1 s) of ACh evoked in a dose-dependent manner (EC 50 = 4.1 μM) a reversible inward current with a long latency (average 1.3 s), at holding potential ( V h ) = −50 mV. This current was reversibly blocked by atropine and mimicked by muscarine. Application of ATP also evoked a reversible inward current at V h = −50 mV, but the current showed two components. A fast component with a short latency was largely reduced when N -methyl- d -glucamine (NMDG) replaced extracellular sodium, implying a P2X-like ionotropic conductance. The second component had a longer latency (average 1.1 s) and was presumably activated by metabotropic P2Y-like receptors. The second component of ATP-evoked current shared similar characteristics with the responses evoked by ACh: the current reversed near 0 mV, displayed inward rectification, could be carried by NMDG, and was insensitive to extracellular and intracellular calcium. This ACh-/ATP-evoked conductance was reversibly inhibited by preapplication of ionomycin. These results suggest that muscarinic receptors and purinergic metabotropic receptors activate a similar large nonselective cation conductance via a common intracellular pathway in SGNs, a candidate mechanism to regulate neuronal excitability of SGNs. acetylcholine adenosine 5′-triphosphate cochlear neuron Footnotes Address for reprint requests and other correspondence: D. Dulon, Laboratoire de Biologie Cellulaire et Moléculaire de l'Audition, INSERM EMI 99–27, Hôpital Pellegrin, Université de Bordeaux 2, 33076 Bordeaux, France (E-mail: didier.dulon@bordeaux.inserm.fr ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. First published December 19, 2001;10.1152/ajpcell.00364.2001 Copyright © 2002 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Cell Physiology The American Physiological Society

Nonselective cation conductance activated by muscarinic and purinergic receptors in rat spiral ganglion neurons

AJP - Cell Physiology , Volume 282 (5): C1121 – May 1, 2002

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References (82)

Publisher
The American Physiological Society
Copyright
Copyright © 2010 the American Physiological Society
ISSN
0363-6143
eISSN
1522-1563
DOI
10.1152/ajpcell.00364.2001
pmid
11940528
Publisher site
See Article on Publisher Site

Abstract

Abstract The present study characterizes the ionic conductances activated by acetylcholine (ACh) and ATP, two candidate neuromodulators, in isolated spiral ganglion neurons (SGNs). Brief application (1 s) of ACh evoked in a dose-dependent manner (EC 50 = 4.1 μM) a reversible inward current with a long latency (average 1.3 s), at holding potential ( V h ) = −50 mV. This current was reversibly blocked by atropine and mimicked by muscarine. Application of ATP also evoked a reversible inward current at V h = −50 mV, but the current showed two components. A fast component with a short latency was largely reduced when N -methyl- d -glucamine (NMDG) replaced extracellular sodium, implying a P2X-like ionotropic conductance. The second component had a longer latency (average 1.1 s) and was presumably activated by metabotropic P2Y-like receptors. The second component of ATP-evoked current shared similar characteristics with the responses evoked by ACh: the current reversed near 0 mV, displayed inward rectification, could be carried by NMDG, and was insensitive to extracellular and intracellular calcium. This ACh-/ATP-evoked conductance was reversibly inhibited by preapplication of ionomycin. These results suggest that muscarinic receptors and purinergic metabotropic receptors activate a similar large nonselective cation conductance via a common intracellular pathway in SGNs, a candidate mechanism to regulate neuronal excitability of SGNs. acetylcholine adenosine 5′-triphosphate cochlear neuron Footnotes Address for reprint requests and other correspondence: D. Dulon, Laboratoire de Biologie Cellulaire et Moléculaire de l'Audition, INSERM EMI 99–27, Hôpital Pellegrin, Université de Bordeaux 2, 33076 Bordeaux, France (E-mail: didier.dulon@bordeaux.inserm.fr ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. First published December 19, 2001;10.1152/ajpcell.00364.2001 Copyright © 2002 the American Physiological Society

Journal

AJP - Cell PhysiologyThe American Physiological Society

Published: May 1, 2002

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