Binding of the cocaine analog 2 beta-[3H] carboxymethoxy-3 beta-(4-fluorophenyl)tropane to the serotonin transporter.

The cocaine analog 2 beta-carboxymethoxy-3 beta-(4-fluorophenyl)-tropane (CFT) binds to platelet plasma membrane vesicles. [3H]CFT binding is blocked equally well by cocaine and imipramine. Specific (cocaine-sensitive) binding requires Na+ and is inhibited by H+ and Cl- ions. At 150 mM Na2SO4 and pH 9.5, the KD for [3H]CFT is 232 +/- 71 nM. The number of specific [3H]CFT binding sites on the membrane vesicles is equal to the number of serotonin transporters, as measured by [3H]imipramine binding. Binding of imipramine and CFT appeared to be mutually competitive. These results suggest that [3H]CFT and cocaine bind to the serotonin transporter at a site close to but distinct from the antidepressant binding site.