Quantitative autoradiography of brain binding sites for the vesicular acetylcholine transport blocker 2-(4-phenylpiperidino)cyclohexanol (AH5183).
2-(4-Phenylpiperidino)cyclohexanol (AH5183) is a noncompetitive and potent inhibitor of high-affinity acetylcholine transport into cholinergic vesicles. It is reported here that [3H]AH5183 binds specifically and saturably to slide-mounted sections of the rat forebrain (Kd = 1.1 to 2.2 X 10(-8) M; Bmax = 286 to 399 fmol/mg of protein). The association and dissociation rate constants for [3H]AH5183 binding are 8.6 X 10(6) M-1 X min-1 and 0.18 min-1, respectively. Bound [3H]AH5183 can be displaced by nonradioactive AH5183 and by the structural analog (2 alpha,3 beta,4A beta,8A alpha)-decahydro-3-(4-phenyl-1-piperidinyl)-2- naphthalenol but not by 10 microM concentrations of the cholinergic drugs acetylcholine, choline, atropine, hexamethonium, eserine, or hemicholinium-3 or by the structurally related compounds 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1-methyl-4-phenylpyridine, (+/-)-N-allylnormetazocine (SKF 10,047), levoxadrol, or dexoxadrol. Quantitative autoradiography reveals that [3H]AH5183 binding sites are distributed heterogenously throughout the rat forebrain and are highly localized to cholinergic nerve terminal regions. At the level of the caudate nucleus-putamen, the highest concentrations of saturable [3H]AH5183 binding (713-751 fmol/mg of protein) are found in the vertical limb of the diagonal band and the olfactory tubercle, with lesser amounts (334-516 fmol/mg of protein) in the caudate-putamen, nucleus accumbens, superficial layers of the cerebral cortex, and the primary olfactory cortex. At day 7 after transsection of the left fimbria, [3H]AH5183 binding and choline acetyltransferase activity in the left hippocampus were reduced by 33 +/- 6% and 61 +/- 7%, respectively. These findings indicate that [3H]AH5183 binds to a unique recognition site in rat brain that is topographically associated with cholinergic nerve terminals.
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D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009467:Neuromuscular Depolarizing Agents / Q000378:metabolism* / Q000494:pharmacology; D010622:Phencyclidine / Q000031:analogs & derivatives* / Q000378:metabolism; D010880:Piperidines; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium
D009467:Neuromuscular Depolarizing Agents; D010880:Piperidines; D011950:Receptors, Cholinergic; D014316:Tritium; C006189:vesamicol; D010622:Phencyclidine; D000109:Acetylcholine