Asymmetric Tc-Nitrido Complexes for Imaging 5HT1A Receptor

The [TcN(PNP)]2+ metal fragment allows the incorporation of a bioactive molecule into a 99mTc-nitrido complex. Herein we describe the first application of this procedure to a 2-methoxyphenyl piperazine (2-MPP) pharmacophore, wich display preferential affinity for the 5HT1A receptors. An N-derivatized cysteine, namely 2-MPPP-cys-OS, where 2-MPPP is 3-[4-(2-methoxyphenyl)piperazin-1-yl]propionate was synthetized as the pharmacophore containing bifunctional-ligand. The asimmetric Tc(V)-nitrido complexes [99g/99m Tc(N)(PNP)(2-MPPP-cys-OS)] (PNP= PNP3, PNP4), were obtained in hig yields (95%), by simultaneous addition of PNP and 2.MPPP-cys-OS ligands to a solution containing a 99mTc-nitrido precursor. Biological evaluation of the complexes were performed by conducting in vitro 5HT1A receptor-binding assays and in vivo biodistribution studies in rats.