Uptake and regional distribution of (+)-(R)- and (−)-(S)-N-[methyl-11C]-nicotine in the brains of Rhesus monkey an attempt to study nicotinic receptors in vivo
N-[methyl-11C] nicotine (11C-nicotine) was given intravenously to monkeys and the uptake and regional distribution of radioactivity was followed in the brain using positron emission tomography (PET). The11C-radioactivity in the brain peaked within 1–2 min and then rapidly declined. Pretreatment with unlabelled nicotine (10 μg/kg) reduced the uptake of11C-radioactivity to the brain by 30%. The uptake of radioactivity was higher following (+)11C-nicotine than (−)11C-nicotine. Both enantiomers were distributed in a similar manner within the brain. When animals were infused with a peripheral nicotinic blocker (trimetaphan) the uptake of radioactivity to the brain was lower following (+)11C-nicotine compared to (−)11C-nicotine. The amount of radioactivity was high in the occipital cortex, thalamus, intermediate in the frontal cortex and low in white matter in (−)11C injected monkeys while no regional difference in distribution of11C-radioactivity was observed after injection of (+)11C-nicotine.
KeywordsMonkey positron emission tomography 11C-nicotine optic enantiomers nicotinic receptors brain regional distribution
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