Displacement of RTI-55 from the dopamine transporter by cocaine

S. John Gatley, Nora D. Volkow, Ruoyan Chen, Joanna S. Fowler, F. Ivy Carroll, Michael J. Kuhar

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10 Scopus citations


The cocaine analog 3β-(4-iodophenyl)tropane-2β-carboxylic acid methyl ester (RTI-55 or βCIT) has a higher affinity for the dopamine transporter and may be potentially useful in interfering with cocaine's actions in brain. However, imaging studies have demonstrated displacement of tracer doses of [123I]RTI-55 by a subsequent dose of cocaine. Similar displacement of pharmacological doses of RTI-55 might compromize therapy with RTI-55 in cocaine abuse. The reduction in dopamine transporter availability, assessed in vivo in mouse striatum using [3H]cocaine, caused by pretreatment with RTI-55 was significantly mitigated by subsequent administration of cocaine. In a similar experiment using a tracer dose of [123I]RTI-55 significant reductions of striatal radioligand binding by pretreatment with cocaine or RTI-55 were not observed. These results suggest that: (1) cocaine can displace pharmacological doses of RTI-55 from striatum, and (2) radioligands used to assess binding site occupancy should have a lower affinity than the occupying drug.

Original languageEnglish
Pages (from-to)145-151
Number of pages7
JournalEuropean Journal of Pharmacology
Issue number2
StatePublished - 25 Jan 1996
Externally publishedYes


  • Cocaine analog
  • Mouse
  • Psychostimulant abuse
  • [I]RTI-55


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