Uptake and binding of the serotonin 5-HT1A antagonist [18F]-MPPF in brain of rats: effects of the novel P-glycoprotein inhibitor tariquidar

Neuroimage. 2010 Jan 15;49(2):1406-15. doi: 10.1016/j.neuroimage.2009.09.048. Epub 2009 Sep 28.


We used microPET to map the dose-response to the novel P-glycoprotein (P-gp) inhibitor tariquidar (TQD) of the initial influx of the P-gp substrate [(18)F]-MPPF in rat brain, and to test for effects of P-gp inhibition on the subsequent binding of [(18)F]-MPPF to serotonin 5-HT(1A) receptors. Summation maps of [(18)F]-MPPF uptake during the first 100 seconds after intravenous injection were calculated in groups of rats with vehicle (glucose 5%) pretreatment, or following pretreatment with TQD at doses of 5, 15, or 30 mg/kg. The early summation image (K(1)-weighted), were validated as a surrogate marker for the physiological blood-brain clearance (K(1); ml g(-)(1) min(-1)) by linear graphic analysis of the unidirectional blood-brain clearance relative to an image-based arterial input measured in the left ventricle of the heart. In the same animals, parametric maps of the [(18)F]-MPPF binding potential (BP(ND)) were calculated from the entire 60-minute emission recordings using conventional reference tissue methods. All [(18)F]-MPPF recordings were followed by an [(18)F]-FDG emission recording, the summation of which was used for spatial normalization to a rat brain atlas. Test-retest variability of K(1)-weighted uptake and BP(ND) was 25%. TQD treatment evoked a global dose-dependent increase in K(1)-weighted summation, which increased 2.5-fold with TQD (30 mg/kg), suggesting an IC(50) of 5 mg/kg TQD. All TQD doses increased the apparent [(18)F]-MPPF BP(ND) calculated by the Logan method by 30%-40%, a bias likely arising due to increased free [(18)F]-MPPF concentrations in brain. TQD (15 mg/kg) evoked a 45% global increase in [(18)F]-FDG uptake, suggesting perturbation of brain energy metabolism due to P-gp blockade.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors*
  • Animals
  • Brain / diagnostic imaging
  • Brain / drug effects*
  • Brain / metabolism
  • Central Nervous System Agents / administration & dosage
  • Central Nervous System Agents / pharmacokinetics
  • Central Nervous System Agents / pharmacology
  • Dose-Response Relationship, Drug
  • Female
  • Piperazines / metabolism*
  • Piperazines / pharmacokinetics
  • Positron-Emission Tomography / methods
  • Pyridines / metabolism*
  • Pyridines / pharmacokinetics
  • Quinolines / administration & dosage
  • Quinolines / pharmacokinetics
  • Quinolines / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Serotonin, 5-HT1A / metabolism
  • Reproducibility of Results
  • Serotonin 5-HT1 Receptor Antagonists*
  • Serotonin Antagonists / pharmacokinetics
  • Serotonin Antagonists / pharmacology
  • Time Factors
  • Ventricular Function, Left


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Central Nervous System Agents
  • Piperazines
  • Pyridines
  • Quinolines
  • Serotonin 5-HT1 Receptor Antagonists
  • Serotonin Antagonists
  • Receptor, Serotonin, 5-HT1A
  • tariquidar
  • 4-(2'-methoxyphenyl)-1-(2'-(N-2'-pyridinyl)-p-(18F)fluorobenzamido )ethylpiperazine