Fig. 7. No variable of the action potential (AP) activity correlated with octopamine-dependent modulation of the transepithelial potential (TEP). (A) Haemolymph Ringer (control) injection only slightly reduced and phase-shifted the TEP oscillation for less than 20 min, while injection of 150 nmol of octopamine caused a long-term depression of TEP oscillations. Flight activity marked the beginning of a non-oscillatory interval. The frequency of both action potential classes was unaffected by control or octopamine injections. (B) None of the evaluated variables of the action potential activity was affected by the injections. The first bin after the control injection (filled circle) is only 5.2 min long.