αConotoxin Arenatus Ib[V11Lv16D] Is A Potent And Selective Antagonist At Rat And Human Native α7 Nicotinic Acetylcholine Receptors

Department

neurobiology

Document Type

Article

Abstract

A recently developed α-conotoxin, α-conotoxin Arenatus IB-[V11l,V16D] (α-CtxArIB[V11L,V16D]), is a potent and selective competitive antagonist at rat recombinant α7 nicotinic acetylcholine receptors (nAChRs), making it an attractive probe for this receptor subtype. α7 nAChRs are potential therapeutic targets that are widely expressed in both neuronal and nonneuronal tissues, where they are implicated in a variety of functions. In this study, we evaluate this toxin at rat and human native nAChRs. Functional α7 nAChR responses were evoked by choline plus the allosteric potentiator PNU-120596 [1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5- methyl-isoxazol-3-yl)-urea] in rat PC12 cells and human SH-SY5Y cells loaded with calcium indicators. α-CtxArIB[V11L,V16D] specifically inhibited α7 nAChR-mediated increases in Ca 2+ in PC12 cells. Responses to other stimuli, 5-I-A-85380 [5-iodo-3-(2(S)-azetidinylmethoxy)pyridine dihydrochloride], nicotine, or KCl, that did not activate α7 nAChRs were unaffected. Human α7 nAChRs were also sensitive to α-CtxArIB[V11L, V16D]; acetylcholine-evoked currents in Xenopus laevis oocytes expressing human α7 nAChRs were inhibited by α-CtxArIB[V11L,V16D] (IC 50 , 3.4 nM) in a slowly reversible manner, with full recovery taking 15 min. This is consistent with the time course of recovery from blockade of rat α7 nAChRs in PC12 cells. α-CtxArIB[V11L,V16D] inhibited human native α7 nAChRs in SHSY5Y cells, activated by either choline or AR-R17779 [(2)-spiro[1-azabicyclo[2.2.2]octane-3,59-oxazolidin]-29-one] plus PNU-120596. Rat brain α7 nAChRs contribute to dopamine release from striatal minces; α-CtxArIB[V11L,V16D] (300 nM) selectively inhibited choline-evoked dopamine release without affecting responses evoked by nicotine that activates heteromeric nAChRs. This study establishes that α-CtxArIB[V11L,V16D] selectively inhibits human and rat native α7 nAChRs with comparable potency, making this a potentially useful antagonist for investigating α7 nAChR functions. Copyright © 2008 by The American Society for Pharmacology and Experimental Therapeutics.

Publication Date

11-1-2008

Publication Title

Journal of Pharmacology and Experimental Therapeutics

ISSN

00223565

Volume

327

Issue

2

First Page

529

Last Page

537

Digital Object Identifier (DOI)

10.1124/jpet.108.142943

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