Bullfrog dorsal root ganglion (DRG) cells were classified into three types, As, Ar and C, according to their electrophysiological properties. Actions of tetraethylammonium (TEA; 100 μM−100 mM) on As-type cells were examined using current- and voltage-clamp methods; TEA caused a membrane depolarization or an inward current, associated with a decrease in membrane conductance. These TEA-induced responses reversed in polarity at −85 to −90 mV, and the change in reversal potential followed the Nernst equation as extracellular K + concentration was changed. The TEA-induced responses were reversibly inhibited by Ca ++-free/high-Mg ++ solutions and inorganic Ca blockers. It is concluded that bullfrog DRG As-type cells might be also endowed with Ca-sensitive K channels which may be open at rest and blocked by TEA.
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