Tritium-labelled hemicholinium-3 ([3H]HC-3): membrane binding properties and potential uses for a novel presynaptic marker in cholinergically-innervated tissues

Sodium-dependent high-affintiy choline uptake (SDHACU) is the primary regulatory step in acetylcholine biosynthesis and subserves an essential function in cholinergically-mediated neurotransmission. Recent studies with [3H]hemicholinium-3 ([3H]HC-3), a potent competitive inhibitor of SDHACU, reveal that closely associated membrane sites mediate high-affinity [3H]HC-3 binding and SDHACU. In this report, supportive evidences for this association are presented and potential uses of [3H]HC-3 are outlined for studies of disorders that involve cholinergic nervous system dysfunction. 40 refs.; 1 figure