Neuroimaging of the vesicular acetylcholine transporter by a novel 4-[18F]fluoro-benzoyl derivative of 7-hydroxy-6-(4-phenyl-piperidin-1-yl)-octahydro-benzo[1,4]oxazines

Nucl Med Biol. 2009 Jan;36(1):17-27. doi: 10.1016/j.nucmedbio.2008.10.006.

Abstract

Phenylpiperidinyl-octahydro-benzo[1,4]oxazines represent a new class of conformationally restrained vesamicol analogues. Derived from this morpholine-fused vesamicol structure, a new fluorine-18-labeled 4-fluorobenzoyl derivative ([(18)F]FBMV) was synthesized with an average specific activity of 75 GBq/micromol and a radiochemical purity of 99%. The radiolabeling method included an exchange reaction of a 4-nitro group of the precursor by fluorine-18, a reduction procedure to eliminate excess of the nitro compound, followed by a high-performance liquid chromatography purification. [(18)F]FBMV demonstrates (i) a moderate lipophilic character with a logD(pH7.0) 1.8+/-0.10; (ii) a considerable binding affinity to the vesicular acetylcholine transporter (VAChT) (K(i)=27.5 nM), as determined using PC12 cells transfected with a VAChT cDNA, and a low affinity to sigma(1,2) receptors (K(i) >3000 nM); (iii) a good uptake into the rat and pig brains; (iv) a typical accumulation in the VAChT-containing brain regions; and (v) an approximately 20% reduction in cortical tracer binding after a specific cholinergic lesion using 192IgG-saporin. [(18)F]FBMV exhibits another PET marker within the group of vesamicol derivatives that demonstrates potentials in imaging brain cholinergic deficits, while its usefulness in clinical practice must await further investigation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoradiography
  • Benzoic Acid / chemistry*
  • Benzoic Acid / metabolism
  • Benzoic Acid / pharmacokinetics
  • Brain / cytology
  • Brain / diagnostic imaging
  • Brain / metabolism*
  • Brain / pathology
  • Female
  • Fluorine Radioisotopes / chemistry*
  • Oxazines / chemistry*
  • PC12 Cells
  • Positron-Emission Tomography
  • Radiochemistry
  • Rats
  • Substrate Specificity
  • Tissue Distribution
  • Vesicular Acetylcholine Transport Proteins / analysis
  • Vesicular Acetylcholine Transport Proteins / metabolism*

Substances

  • Fluorine Radioisotopes
  • Oxazines
  • Vesicular Acetylcholine Transport Proteins
  • Benzoic Acid