In vivo specific binding of [3H]1-nicotine in the mouse brain.
[3H] 1-Nicotine was used as a receptor ligand in the intact mouse. It was injected i.v., and radioactivity in brain regions was assayed. Nonspecific binding was estimated by pretreatment with unlabelled 1-nicotine. Radioactivity entered the brain rapidly, was heterogeneously distributed, and declined after 5 min. Estimated specific binding was highest in the medial and posterior cortex, midbrain, thalamus/hypothalamus and medulla/pons; intermediate in the cerebellum, caudate/putamen, frontal and frontoparietal cortex; and lowest in the hippocampus and olfactory bulb. Autoradiography showed similar patterns. Coinjection of unlabelled 1-nicotine reduced specific binding so that it approached estimated nonspecific binding. Nicotinic agonists reduced radioactivity in the thalamus/hypothalamus, but nicotinic antagonists were less active. Non-nicotinic drugs did not reduce brain radioactivity. The results suggest that radiolabelled nicotine may be used for in vivo receptor studies despite problems in estimating nonspecific binding.
Broussolle
E P
EP
Addition Research Center, National Institute on Drug Abuse, Baltimore, MD 21224.
Wong
D F
DF
Fanelli
R J
RJ
London
E D
ED
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009538:Nicotine / Q000378:metabolism*; D013997:Time Factors; D014018:Tissue Distribution; D014316:Tritium
D014316:Tritium; D009538:Nicotine