Fig. 6. (A,B) Action potential variables during oscillatory and non-oscillatory intervals of the transepithelial potential (TEP). (A) The upper panel shows the time course of the TEP and flight activity, while the lower panels illustrate the action potential activity of the small and large action potentials (APs), evaluated in bins of 10 s. Periods of elevated action potential activity and quiescent periods occurred independently of the TEP and of flight activity, during oscillatory as well as during non-oscillatory intervals. (B) No correlation between the phase of the TEP oscillations and any evaluated variable of the action potential activity was found. All variables were analyzed in bins of 10 min and plotted on the same time axis as in A. The frequency of the small action potentials was more variable than that of the large ones (Table 3). The percentage of action potentials that were members of bursts fluctuated randomly between <25 and >75 %. Similarly, the mean number of action potentials in each burst and the coefficient of variation (CV) did not exhibit any correlation with the time course of the TEP. The dashed line marks a CV of 1, which would indicate a random distribution of the action potentials.