Fig. 1. Time courses of the transepithelial voltage (V_te) of the anterior stomach of a fourth-instar mosquito larva (Aedes aegypti). At arrow 1, the perfusion pipette was inserted into the anterior end of the anterior midgut. At arrow 2, the preparation was fixed on the pipette with a fine hair. At arrows 3–7, small slices (each approximately 10% of the initial length of the preparation) were cut off the open, posterior end of the preparation. At arrow 8, the remnant of the preparation was withdrawn from the pipette. During the time period indicated by the horizontal box, 0.2 µmol l^-1 serotonin was present in the bathing medium. Infusion mode was used throughout the experiments shown.