Fig. 3. (A) Representative scan of tetraethylammonium (TEA) flux at locations along the lower Malpighian tubule (LMT) and ureter. Tubules were bathed in saline containing 100 µmol l^–1 TEA. The length of each arrow corresponds to the magnitude of TEA influx and the axis of each arrow indicates the axis of the TEA-SeR microelectrode's movement. (B) TEA influx (left ordinate) and differential signal (right ordinate) in the LMT, distal ureter and proximal ureter. The proximal ureter is defined as the 50% of the ureter length closest to the gut. Each bar shows mean + S.E.M. for N=6 preparations.