title: Ligand Selectivity among the Dopamine and Serotonin Transporters Specified by the Forward Binding Reaction.
abstract: The membrane transporters for the monoamines serotonin (SERT) and dopamine (DAT) are prominent targets of various psychoactive substances, including competitive inhibitors, such as tricyclic antidepressants, methylphenidate, and cocaine. Upon rapid application of a substrate, SERT and DAT display an inwardly directed current comprised of a peak and a steady-state component. Binding of a competitive inhibitor to the transporter leads to reduction of the peak current amplitude because occupancy of the transporter by an inhibitor prevents the induction of the peak current by the substrate. We show that the inhibitory effect on the peak current can be used to study the association rate constant (k(on)), dissociation rate constant (k(off)), and equilibrium dissociation constant (K(D)) of chemically distinct SERT and DAT inhibitors, with high temporal precision and without the need of high-affinity radioligands as surrogates. We exemplify our approach by measuring the kinetics of cocaine, methylphenidate, and desipramine binding to SERT and DAT. Our analysis revealed that the selectivity of methylphenidate and desipramine for DAT and SERT, respectively, can be accounted for by their rate of association and not by the residence time in their respective binding sites.
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Peter S
authors: PS
authors: Hasenhuetl
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Klaus
authors: K
authors: Schicker
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Xaver
authors: X
authors: Koenig
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Yang
authors: Y
authors: Li
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Subhodeep
authors: S
authors: Sarker
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Thomas
authors: T
authors: Stockner
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Sonja
authors: S
authors: Sucic
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Harald H
authors: HH
authors: Sitte
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.).
authors: Michael
authors: M
authors: Freissmuth
authors: Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria (P.S.H., K.S., X.K., Y.L., Su.S., T.S., So.S., H.H.S., M.F., W.S.) walter.sandtner@meduniwien.ac.at.
authors: Walter
authors: W
authors: Sandtner
mesh_terms: D001665:Binding Sites; D003042:Cocaine / Q000493:pharmacokinetics; D003891:Desipramine / Q000493:pharmacokinetics; D050483:Dopamine Plasma Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008774:Methylphenidate / Q000493:pharmacokinetics; D014179:Neurotransmitter Uptake Inhibitors / Q000493:pharmacokinetics*; D018408:Patch-Clamp Techniques / Q000379:methods; D050486:Serotonin Plasma Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D014179:Neurotransmitter Uptake Inhibitors; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D008774:Methylphenidate; D003042:Cocaine; D003891:Desipramine