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Published on: November 21, 2012

D2 dopamine receptor internalization prolongs the decrease of radioligand binding after amphetamine: a PET study in a

Mette Skinbjerg1, Jeih-San Liow, Nicholas Seneca

  • 1Molecular Imaging Branch, National Institute of Mental Health, Bethesda, MD, USA.

Neuroimage
|January 26, 2010
PubMed
Summary
This summary is machine-generated.

Amphetamine causes a prolonged decrease in dopamine D(2) receptor binding. This study shows receptor internalization, not dopamine displacement, is responsible, using arrestin3 knockout mice and PET imaging.

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Area of Science:

  • Neuroscience
  • Pharmacology
  • Molecular Biology

Background:

  • Amphetamine acutely increases extracellular dopamine, leading to decreased in vivo binding of dopamine D(2) receptor PET radioligands.
  • This radioligand binding deficit persists long after dopamine levels normalize, suggesting a mechanism beyond simple dopamine displacement.

Purpose of the Study:

  • To investigate whether receptor internalization causes the prolonged decrease in dopamine D(2) receptor radioligand binding after amphetamine administration.
  • To differentiate between dopamine displacement and receptor internalization as the cause of this phenomenon.

Main Methods:

  • Utilized wild-type and arrestin3 (arr3) knockout mice, which lack the capacity for D(2) receptor internalization.
  • Employed positron emission tomography (PET) with two D(2) selective radioligands: [(11)C]MNPA (agonist) and [(18)F]fallypride (antagonist).
  • Scanned mice at baseline, 30 minutes, and 4 hours after amphetamine administration (3 mg/kg, i.p.).

Main Results:

  • At 30 minutes post-amphetamine, both radioligands showed displacement, with no significant difference between wild-type and arr3 knockout mice.
  • At 4 hours, radioligand binding returned to baseline in arr3 knockout mice but remained decreased in wild-type mice.
  • Retest scans showed unaltered radioligand binding, confirming the observed effects were specific to amphetamine treatment.

Conclusions:

  • The prolonged reduction in dopamine D(2) receptor binding after amphetamine is primarily caused by receptor internalization, not dopamine displacement.
  • This study highlights the utility of small animal PET for in vivo investigation of receptor trafficking in genetically modified models.