Fig. 8.

DAT-mediated [³H]MPP⁺ efflux experiments. As described under Materials and Methods, synaptosomes were preloaded with [³H]MPP⁺ for 60 min. Various concentrations of d-amphetamine were then added, and samples were filtered at various times up to 60 min later. Each value is the mean ± S.D. The data of three independent experiments were pooled and fit to one- and two-component dissociation experiments using MLAB-PC. In all cases, the two-component model fit significantly better than the one-component model (F-test, P < 0.002). The best-fit estimates of the kinetic parameters are reported in Table 3.