Voltage-activated fast currents of frog optic tectum neurones are blocked by ouabain or K(+)-free solution.
Frog optic tectum neurones in vitro (under whole cell patch clamp with a Cs(+)-filled electrode) generated, in response to voltage steps negative to -80 mV from -60 mV holding potential, transient inward currents dependent on extracellular Na+ and blocked by tetrodotoxin (TTX). Depolarizing steps from the same holding potential induced conventional, fast Na+ currents followed by a transient outward cationic current (Icat). Voltage-activated Na+ currents (induced by negative or positive steps) and Icat were blocked by ouabain or K(+)-free solution with comparable timecourse. It is suggested that transient inward and outward currents of frog tectal neurones were at least partly dependent on the rapid operation of a membrane cation transporter.
Zaykin
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Biophysics Sector, International School for Advanced Studies (S.I.S.S.A.), Trieste, Italy. nistri@sissa.it
Nistri
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D000818:Animals; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects; D011893:Rana esculenta; D013477:Superior Colliculi / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D013779:Tetrodotoxin; D010042:Ouabain