Figure 4.

Alleviation by aptamer II-3 of receptor inhibition by cocaine. The whole-cell current corrected for receptor desensitization was determined by using the cell-flow technique (22, 35). At a constant concentration of 100 μM carbamoylcholine, the ratio of the maximum current amplitude obtained in the absence, A, and presence, A_I, of a constant concentration (150 μM) of cocaine was determined as a function of the concentration of aptamer II-3. The cells were preequilibrated with aptamer II-3 for 2 s. Each data point represents the average of two to three experiments by using on the average two cells per point. Eq. III-A was used to evaluate K_I(obs) = 98 ± 23 μM; K_II(obs) = 177 ± 40 μM; and K_A(obs) = 0.7 ± 0.1 μM. The experimental conditions were as described in Fig. 2 legend and Materials and Methods.