The Journal of General Physiology
INTRODUCTION [email protected] Correspondence toStefanGründer: by acetylcholine(McIntoshetal.,1999),serotonin (Terlau andOlivera,2004).Theyinhibit channelsgated channels aretheconotoxinsproducedbyconesnails main groupoftoxinsthatinteractwithligand-gatedion that interactwithdifferentclassesofionchannels.The sea anemones,containarichdiversityofproteintoxins potential. by continuousdepolarizationabovethethreshold the steady-stateinactivationofvoltage-gatedchannels ligand concentrationsabovethreshold,isanalogousto This steady-statedesensitizationofASICs,inducedby Alvarez De La chronically desensitizeASICs(Bensonetal.,1999; concentrations, forexampleduringmetabolicacidosis, activ are closetothethresholdconcentrationneeded contrast tootherligands,restingconcentrationsofH the acid-sensingionchannels(ASICs).However, in H 1998). Theapparentaffinityoftheseionchannelsfor (Waldmann etal.,1997;Waldmann andLazdunski, H upon anincreaseintheextracellularconcentrationof channels haverecentlybeencharacterizedthatopen H (ASIC) 1abyIncreasing ItsApparent H The Tarantula Toxin Psalmotoxin1InhibitsAcid-sensingIonChannel establishing H (Waldmann andLazdunski,1998;Bässleretal.,2001), kinetics iscomparablewithotherligand-gatedchannels oue16Nme uy20 71–79 July2005 Number1 Volume 126 J. Gen.Physiol. ©TheRockefellerUniversity Press http://www.jgp.org/cgi/doi/10.1085/jgp.200509303