Figure 2.

Inhibitory effect of (-)-221I on ACh-induced currents in X. laevis oocytes expressing recombinant nicotinic receptors. Currents were recorded in the voltage-clamp mode at -60 mV. Concentrations of ACh used were 1 μM for the α4β2 receptor and 100 μM for the α7 receptor. For test responses, oocytes were preincubated with (-)-221I for 3 min and then exposed to ACh with (-)-221I. A, representative traces showing the ACh-elicited currents in the absence and presence of (-)-221I (3 μM). Horizontal bars indicate the period of perfusion with ACh for 5 s. Vertical scale bars represent 0.5 μA on the α4β2 receptor, and 0.1 μA on the α7 receptor. B, concentration-response curves for (-)-221I on recombinant nicotinic receptors. Current responses to ACh in the presence of (-)-221I in each oocyte were normalized to the ACh responses (control responses) recorded in the same oocytes. Values represent the mean ± S.E.M. for five separate experiments.