title: Further studies on the biochemical characterization and autoradiographic distribution of [3H]hemicholinium-3 binding sites in rat brain: a presynaptic cholinergic marker.
abstract: Hemicholinium-3 (HC-3) is a potent inhibitor of the high-affinity choline uptake system (HACU). Here we report on the biochemical characterization and autoradiographic distribution of [3H]hemicholinium-3 binding sites in rat brain, confirming and expanding results from previous studies. The binding of [3H]HC-3 to striatal membranes was specific, to a single site, sodium-dependent, saturable, and of high-affinity, Kd values being about 3 nM for striatum, 5 nM for the hippocampus and 12 nM for neocortex. [3H]HC-3 specific binding exhibited a pharmacological profile suggestive of physiologically relevant interactions and fully comparable to that reported for HACU. The uneven distribution of [3H]HC-3 binding sites exhibited a high degree of correspondence with the reported distribution of HACU and other enzymatic presynpatic cholinergic markers. The punctual differences between our study and previous works on [3H]HC-3 binding are analysed. We conclude that [3H]HC-3 labelling may be used as a selective and quantifiable marker of the cholinergic presynaptic terminals in close relationship with HACU.
authors.affiliation: Department of Physiology and Pharmacology, University Hospital, Marqués de Valdecilla, University of Cantabria, Santander, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Pascual
authors.forename: A M
authors.initials: AM
authors.lastname: Gonzalez
authors.forename: A
authors.initials: A
authors.lastname: Pazos
mesh_terms: D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism; D003342:Corpus Striatum / Q000737:chemistry* / Q000378:metabolism; D006426:Hemicholinium 3 / Q000378:metabolism*; D006624:Hippocampus / Q000737:chemistry* / Q000378:metabolism; D010277:Parasympathomimetics / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010277:Parasympathomimetics; D006426:Hemicholinium 3