A comparison of the binding of nicotine and nornicotine stereoisomers to nicotinic binding sites in rat brain cortex |
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| Authors: | J. R. Copeland A. Adem P. Jacob III A. Nordberg |
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| Affiliation: | (1) Department of Pharmacology, Uppsala University, S-75124, P.O.Box 591, Uppsala, Sweden;(2) Division of Clinical Pharmacology and Therapeutics, Department of Medicine, San Francisco General Hospital, San Francisco, CA, USA;(3) Department of Pharmacology and Toxicology, Medical College of Virginia, MCV Station, Box 613, 23298 Richmond, VA, USA |
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| Abstract: | Summary 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.Send offprint requests to A. Nordberg at the above address |
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| Keywords: | Nicotine Nornicotine Stereoisomers Nicotinic receptors Rat brain |
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