ARGIOPINEBLOCKS GLUTAMATE-ACTIVATEDSINGLE-CHANNEL CURRENTS ON CRAYFISHMUSCLE BY TWO MECHANISMS

SUMMARY 1.Theeffect ofthespider venomargiopine onL-glutamate-activated membrane channels ofcrayfish muscle wasinvestigated using thepatch-clamp technique. 2.When10-2M-glutamate and10-9M-argiopine werecontained inthepipette solution ofacell-attached patch, bursts ofopenings ofexcitatory channels appeared after formation ofthepatch. Thesebursts ceased abruptly after variable periods of timeintherangeof5min.Higher concentrations ofargiopine (upto10-6 M)blocked morerapidly, approximately inproportion toconcentration. 3.Theblock ofexcitatory channels could bepartially orcompletely reversed by hyperpolarizing themembranebyupto- 190mV fromtheresting potential. The timeconstant oftherecovery ofchannel opening decreased withincreasing hyperpolarization andwas2mswith-160mV hyperpolarization.