Figure 8. Mean lumen negative transepithelial voltages (V_te; - S.E.M.) of 5 anterior midguts stimulated with serotonin (0.2 μmol l⁻¹) before (white bar) and after substitution of Cl⁻ in the lumen (light grey bar) and on both sides of the tissue (dark grey bar), and photographs of a representative preparation of the anterior midgut of larval (4^th instar) Aedes aegypti identical times after perfusion stop in presence (left) and absence (right) of Cl⁻ on both sides of the tissue. Before V_te and alkalinization after both manipulations were recorded, the tissues were exposed to the new condition for an average of 10 minutes. Asterisk: Mean V_te significantly different from the control (P < 0.05).