Vesamicol and some of its derivatives: questionable ligands for selectively labelling acetylcholine transporters in rat brain.

Presynaptic cholinergic markers could be used for estimating the integrity of the cholinergic systems in the human brain with brain imaging techniques such as Single-photon emission computed tomography (SPECT). Vesamicol, an inhibitor of the vesicular acetylcholine transporter, and some of its derivatives have been suggested as potential ligands for this purpose. However, vesamicol binds not only to acetylcholine transporters but also to sigma binding sites.