Fig. 3. Transepithelial potential (TEP) of the upper, secretory segment of the Malpighian tubules. (A) Representative recording showing the effects of 1 µmol l^–1 ZooneDH (arrow). Three distinct phases of the response are numbered on the trace. The dotted line indicates a potential of 0 mV, when both microelectrodes were placed in the bathing droplet. (B) The mean ± s.e.m. (N=5) TEP prior to the addition of ZooneDH (Rest) and during the three phases of the response. (C) Representative recording showing the effects of 0.1 µmol l^–1 RhoprDH₃₁ (solid arrow) and 1 µmol l^–1 5HT (dashed arrow). The three phases of the TEP response to 5HT are numbered. (D) The mean ± s.e.m. (N=5) TEP prior to the addition of RhoprDH₃₁ (Rest), 10 min after the addition of RhoprDH₃₁ (DH₃₁), and during the three phases of the 5HT response. Asterisks denote a significant difference from the resting TEP (ANOVA, followed by Tukey–Kramer).