Fig. 3. Time course of the effects of 0.3 mmol l^-1 cyanide (KCN) on the basolateral membrane voltage (V_bl), input resistance (R_pc), and the virtual active transport current (I_at(virt)) in a representative principal cell, and on intracellular ATP concentrations [ATP]_i in 6-16 sets of five Malpighian tubules each. Values are mean ± S.E.M. (number of tubule sets). The temporal relationship between the electrical variables and [ATP] are approximate because exchanging the peritubular medium to include CN took 43 s in the electrical assay and 10 s in the ATP assay.