Dopamine D(2) receptor quantification in extrastriatal brain regions using [(123)I]epidepride with bolus/infusion

L H Pinborg, C Videbaek, G M Knudsen, C G Swahn, C Halldin, L Friberg, O B Paulson, Niels Alexander Lassen

21 Citations (Scopus)

Abstract

The iodinated benzamide epidepride, which shows a picomolar affinity binding to dopamine D(2) receptors, has been designed for in vivo studies using SPECT. The aim of the present study was to apply a steady-state condition by the bolus/infusion approach with [(123)I]epidepride for the quantification of striatal and extrastriatal dopamine D(2) receptors in humans. In this way the distribution volume of the tracer can be determined from a single SPECT image and one blood sample. Based on bolus experiments, an algorithm using conventional convolution arguments for prediction of the outcome of a bolus/infusion (B/I) experiment was applied. It was predicted that a B/I protocol with infusion of one-third of the initial bolus per hour would be appropriate. Steady-state conditions were attained in extrastriatal regions within 3-4 h but the infusion continued up to 7 h in order to minimize the significance of individual differences in plasma clearance and binding parameters. A steady-state condition, however, could not be attained in striatal brain regions using a B/I protocol of 20 h, even after 11 h. Under near steady-state conditions a striatal:cerebellar ratio of 23 was demonstrated. Epidepride has a unique signal-to-noise ratio compared to [(123)I]IBZM but present difficulties for steady-state measurements of striatal regions. The bolus/infusion approach is particularly feasible for quantification of the binding potential in extrastriatal regions.
Original languageEnglish
JournalSynapse (New York)
Volume36
Issue number4
Pages (from-to)322-9
Number of pages8
ISSN0887-4476
DOIs
Publication statusPublished - 15 Jun 2000

Keywords

  • Adult
  • Aged
  • Benzamides
  • Brain
  • Contrast Media
  • Homeostasis
  • Humans
  • Iodine Radioisotopes
  • Male
  • Middle Aged
  • Pyrrolidines
  • Receptors, Dopamine D2
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon

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