Abstract 1-(trans-[123 I] Iodopropen-2-yl)-4-(4-cyanophenoxymethyl) piperidine has been prepared as a novel sigma receptor ligand for SPECT. This ligand was found to be selective in vitro for the sigma receptor site (Ki (σ)= 21.7 nM) when tested in a variety of neuroreceptor binding assays. The lipophilicity of this ligand (log P 7.5= 3.36) is appropriate for good brain uptake and relatively low non-specific binding. Radioiodination was accomplished using ...