Table 5.
Equal inhibition by equilibrated cocaine ofm-tyramine uptake and m-tyramine-induced DA efflux
| [Cocaine] (μm) | m-Tyramine uptake (pmol/sec/mg) | DA efflux (pmol/sec/mg) | Efflux/uptake Ratio |
|---|---|---|---|
| 0 | 10.7 ± 0.3 | 1.66 ± 0.08 | 0.16 ± 0.01 |
| 1 | 8.7 ± 0.6 | 1.43 ± 0.08 | 0.16 ± 0.01 |
| 3 | 6.8 ± 0.6 | 1.08 ± 0.03 | 0.16 ± 0.02 |
| 10 | 4.4 ± 0.6 | 0.62 ± 0.04 | 0.15 ± 0.02 |
| IC50 | 6.25 ± 0.28 | 5.93 ± 0.38 | |
| Hi | 0.83 ± 0.04 | 1.00 ± 0.05 |
Cells were preloaded with 84 μm DA. Cocaine was added to the medium for 6 min followed by an addition ofm-tyramine (3 μm). IC50 values and Hill numbers were computed by nonlinear fitting the data with logistic equation. The competitive Ki for cocaine to inhibit m-tyramine-induced DA efflux (see Table 3 for method) was 2.57 ± 0.36 μm. The values are means ± SE of four experiments.