Fig. 6.

Bupropion-induced inhibition of [³H]ibogaine binding to hα3β4 AChRs in the resting (□) and desensitized (○) states, respectively. hα3β4 AChR membranes (1.5 mg/mL) were pre-incubated (30 min) with 16.6 nM [³H]ibogaine in the absence (receptors are mainly in the resting state) and presence of 1 μM (−)-nicotine (receptors are mainly in the desensitized state), and then equilibrated with increasing concentrations of bupropion. Nonspecific binding was determined at 100 μM (−)-ibogaine. The plots are combinations of two experiments, each performed in triplicate, where the error bars are the S.D. The IC₅₀ and n_H values were obtained by nonlinear least-squares fit of the plots (r² = 0.95 for both). The K_i values, calculated using eq. 1 and summarized in Table 3, indicated that bupropion binds to desensitized hα3β4 AChRs with higher affinity than that at resting receptors (Student t-test p = 0.001).