Single-channel recordings of chloride currents in primary cultured Drosophila neurons

Single-chloride-channel currents were recorded from primary cultured Drosophila neurons by means of the gigaohm-seal patch-clamp technique. Small inward-going current channels were observed in excised inside-out patches with the external face of the membrane exposed to bathing solutions devoid of K⁺, Na⁺, and Ca²⁺. The inward current was affected by changing the anions but not the cations bathing the cytoplasmic face of the patch. Complete replacement of CI^? by glutamate eliminated the current. The current was maintained with intracellular solutions containing NO₃^? in place of CI^?. The single-channel conductance was estimated to be 7 ps with CI^?, and 11 ps with NO₃^? at 10°C. Possible functions of this anion-selective channel have been discussed.