title: A comparison of the binding of nicotine and nornicotine stereoisomers to nicotinic binding sites in rat brain cortex.
abstract: Both stereoisomers of nicotine and nornicotine were tested for their ability to competitively displace 3H-(-)-nicotine and 3H-acetylcholine (in the presence of atropine), in rat cortex tissue. 3H-acetylcholine was displaced from two binding sites, super-high and high, by (+)-nicotine, (-)-nornicotine and (+)-nornicotine but from a high affinity site by (-)-nicotine. 3H-nicotine was displaced from two sites, high and low affinity by nicotine and nornicotine stereoisomers. The high-affinity 3H-(-)-nicotine binding site showed similar binding characteristics to one of the sites labelled by 3H-acetylcholine. IC50 values showed (-)-nicotine to be 13 and 25-fold more potent than (+)-nicotine for displacing 3H-(-)-nicotine and 3H-acetylcholine, respectively, but no difference was observed for nornicotine stereoisomers. While (-)-nicotine preferentially bound to the high affinity site of 3H-(-)-nicotine (+)-nicotine preferred the low affinity site. The study provides further evidence for multiple nicotine receptors in brain.
authors.affiliation: Department of Pharmacology, Uppsala University, Sweden.
authors.forename: J R
authors.initials: JR
authors.lastname: Copeland
authors.forename: A
authors.initials: A
authors.lastname: Adem
authors.forename: P
authors.initials: P
authors.lastname: Jacob
authors.forename: A
authors.initials: A
authors.lastname: Nordberg
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D002540:Cerebral Cortex / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009538:Nicotine / Q000031:analogs & derivatives* / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D011978:Receptors, Nicotinic; D009538:Nicotine; C005311:nornicotine