Fig. 1.

Voltage dependence of potentiation and inhibition by dFBr. Membrane potential was increased in 10-mV steps from −100 to +20 mV using a two-electrode voltage clamp on α4β2 nAChR-expressing oocytes. Responses were obtained as discussed under Materials and Methods and normalized to those elicited by application of 1 mM ACh at −60 mV from the same oocyte. At least two batches of oocytes from different frogs were harvested for the experiments. Each data point represents at least n ≥4 replicates with error bars shown as ± S.E.M. For the control group (100 μM cytisine) the relationship between the induced response and the applied membrane potential is linear over the entire range of membrane potentials. Potentiating concentrations of dFBr (10 μM) coapplied with 100 μM cytisine show a similar linear relationship. Coapplication of 30 μM dFBr (inhibitory concentration) with 100 μM cytisine shows a nonlinear relationship between membrane potential and the induced response.