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Background

The sigma-1 receptor is of increasing relevance to neuropsychiatric function and illness (Leonard 2004).[123I] TPCNE (1 (trans-[123I] iodopropen-2-yl)-4-[(4-cyanophenoxy) methyl] piperidine; Ki= 0.67 nM; log P= 3.36) is a novel SPET ligand for the sigma-1 receptor which has demonstrated high selectivity and potency for the receptor in pre-clinical studies (Waterhouse et al 1997). Haloperidol is an antipsychotic drug known to be a potent antagonist of the sigma-1 receptor. Here we have used a pre-dose haloperidol challenge to validate the specific binding of [123I] TPCNE binding in healthy volunteers.

Method

Seven healthy volunteer subjects were recruited (2 female, 5 male, mean age= 31, range= 20–52). Three of the subjects (1 female, 2 male, mean age= 30 range= 22–40) received an oral dose of haloperidol (2.5 mg) approximately 1 h prior to the commencement of the scan. All subjects were …