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Neuropharmacology. 2004 Jun;46(8):1141-57.

Subsets of acetylcholine-stimulated 86Rb+ efflux and [125I]-epibatidine binding sites in C57BL/6 mouse brain are differentially affected by chronic nicotine treatment.

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Institute for Behavioral Genetics, UCB447, University of Colorado, 1480 30th Street, Boulder, CO 80309, USA.


Nicotinic cholinergic receptor (nAChR) sites that bind nicotine with high affinity (likely alpha4beta2-nAChR) increase following chronic nicotine treatment. Effects of chronic treatment on other nAChR binding sites and functional responses of nAChRs are less well studied. Therefore, C57BL/6 mice were intravenously infused for 10 days with saline or nicotine (five doses, 0.25-4.0 mg/kg/h) and nAChR function and three different nicotinic binding sites in 12 brain regions were assessed. Plasma nicotine and cotinine increased linearly with dose. 86Rb+ efflux with higher sensitivity to acetylcholine tended to decrease with increasing dose, whereas efflux with lower sensitivity to acetylcholine tended to increase. As anticipated, likely alpha4beta2-nAChR [125I]-epibatidine binding sites increased with treatment (estimated dosage for one-half maximal increase was 0.44 mg/kg/h, plasma nicotine approximately 20 ng/ml). 86Rb+ efflux with higher sensitivity to acetylcholine and cytisine-sensitive [125I]-epibatidine binding are predominantly alpha4beta2-nAChR. A high correlation between these parameters was observed across brain regions and slopes of these regression lines decreased with treatment dose, suggesting a decrease in function per unit receptor. Likely alpha3beta4-nAChR binding sites were unaffected even at the highest dose (4.0 mg/kg/h, approximately 210 ng/ml). A third set of diverse nAChR binding sites increased in some brain regions, but only after high-dose treatment.

[Indexed for MEDLINE]

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