Studies of the biogenic amine transporters 15. Identification of novel allosteric dopamine transporter ligands with nanomolar potency

J Pharmacol Exp Ther. 2015 Jun;353(3):529-38. doi: 10.1124/jpet.114.222299. Epub 2015 Mar 18.


Novel allosteric modulators of the dopamine transporter (DAT) have been identified. We have shown previously that SRI-9804 [N-(diphenylmethyl)-2-phenyl-4-quinazolinamine], SRI-20040 [N-(2,2-diphenylethyl)-2-phenyl-4-quinazolinamine], and SRI-20041 [N-(3,3-diphenylpropyl)-2-phenyl-4-quinazolinamine] partially inhibit [(125)I]RTI-55 ([(125)I]3β-(4'-iodophenyl)tropan-2β-carboxylic acid methyl ester) binding and [(3)H]dopamine ([(3)H]DA) uptake, slow the dissociation rate of [(125)I]RTI-55 from the DAT, and allosterically modulate d-amphetamine-induced, DAT-mediated DA release. We synthesized and evaluated the activity of >500 analogs of these ligands and report here on 36 selected compounds. Using synaptosomes prepared from rat caudate, we conducted [(3)H]DA uptake inhibition assays, DAT binding assays with [(3)H]WIN35428 ([(3)H]2β-carbomethoxy-3β-(4-fluorophenyl)tropane), and DAT-mediated release assays with either [(3)H]MPP(+) ([(3)H]1-methyl-4-phenylpyridinium) or [(3)H]DA. We observed three groups of [(3)H]DA uptake inhibitors: 1) full-efficacy agents with a one-site fit, 2) full-efficacy agents with a two-site fit, and 3) partial-efficacy agents with a one-site fit-the focus of further studies. These agents partially inhibited DA, serotonin, and norepinephrine uptake, yet were much less potent at inhibiting [(3)H]WIN35428 binding to the DAT. For example, SRI-29574 [N-(2,2-diphenylethyl)-2-(imidazo[1,2-a]pyridin-6-yl)quinazolin-4-amine] partially inhibited DAT uptake, with an IC50 = 2.3 ± 0.4 nM, without affecting binding to the DAT. These agents did not alter DAT-mediated release of [(3)H]MPP(+) in the absence or presence of 100 nM d-amphetamine. SRI-29574 had no significant effect on the d-amphetamine EC50 or Emax value for DAT-mediated release of [(3)H]MPP(+). These studies demonstrate the existence of potent DAT ligands that partially block [(3)H]DA uptake, without affecting DAT binding or d-amphetamine-induced [(3)H]MPP(+) release. These compounds may prove to be useful probes of biogenic amine transporter function as well as novel therapeutics.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • 1-Methyl-4-phenylpyridinium / pharmacology
  • Animals
  • Binding, Competitive / drug effects
  • Caudate Nucleus / drug effects
  • Caudate Nucleus / metabolism
  • Cocaine / analogs & derivatives
  • Cocaine / pharmacology
  • Dextroamphetamine / pharmacology
  • Dopamine / metabolism
  • Dopamine Plasma Membrane Transport Proteins / drug effects*
  • Dopamine Uptake Inhibitors / pharmacology
  • Ligands
  • Male
  • Rats
  • Synaptosomes / drug effects
  • Synaptosomes / metabolism


  • Dopamine Plasma Membrane Transport Proteins
  • Dopamine Uptake Inhibitors
  • Ligands
  • 2beta-carbomethoxy-3beta-(4-iodophenyl)tropane
  • (1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester
  • Cocaine
  • 1-Methyl-4-phenylpyridinium
  • Dextroamphetamine
  • Dopamine