Fig. 2.

Ligand-specific activation or desensitization of α4β2-nAChR. SH-EP1-hα4β2 cells stably expressing functional, human α4β2-nAChRs from loose subunits were subjected to acute challenges for 5 minutes with the indicated drugs at the specified concentrations (abscissa; log M scale) for determination of specific ⁸⁶Rb⁺ efflux (defined in Materials and Methods) (ordinate; % of control response to a full agonist, 1 mM carbamylcholine). (A) Acute response to Saz-A (●). (B) Acute response to A-85380 (●). (C) Acute response to Saz-A after 10-minute pretreatment with 3.16 nM Saz-A (♦) or A-85380 (◇). (D) Acute response to A-85380 after 10-minute pretreatment with 3.16 nM Saz-A (♦) or A-85380 (◇). Results were fit to unconstrained, one- or two-site logistic equations. The derived logEC₅₀ values, Hill coefficients, and fractional contributions of each site (in the case of two-site fits) are reported in the text.