Fig. 3. Representative time course of the short-circuit current (I_sc) across a split distal lamella of a posterior gill with NaCl saline on both sides. The following manipulations were performed: 1, substitution of Cl^– on both sides of the preparation; 2, substitution of Na⁺ on both sides of the preparation; 3, addition of ouabain (2 mmol l^–1) to the internal bathing medium; 4, addition of dimethylsulphoxide (DMSO, 0.2 %) to the internal medium; 5, addition of diphenylamine-2-carboxylate (1 mmol l^–1, dissolved in DMSO) to the internal medium; 6, addition of acetazolamide (0.2 mmol l^–1) to the internal bathing medium. The vertical current deflections are due to short voltage pulses and reflect the preparation conductance (G_te; see lower right corner for scale).