Synthesis and brain regional distribution of [¹¹C]NPS 1506 in mice and rat: An N-methyl-D-aspartate (NMDA) receptor antagonist

NPS 1506 [3-fluoro-γ-(3-fluorophenyl)-N-methylbenzenepropamine] is representative of a non-psychotomimetic class of N-methyl-D-aspartate (NMDA) receptor antagonists. [¹¹C]NPS 1506 was prepared at high radiochemical purity (γ98%) with a specific activity of around 50 GBq/μmmol at the end of synthesis by methylation of the desmethyl precursor with [¹¹C]methyl iodide in the presence of NaH. Biodistribution of [¹¹C]NPS 1506 in mice and rat demonstrated that uptake into the brain was rapid and occurred at high levels. [¹¹C]NPS 1506 showed no appreciable specific binding in rodent brains under in vivo conditions, possibly because of both a large non-specific bound fraction and low in vitro binding affinity for NMDA receptors.