Deletion of the beta 2 nicotinic acetylcholine receptor subunit alters development of tolerance to nicotine and eliminates receptor upregulation
- 2 July 2005
- journal article
- research article
- Published by Springer Science and Business Media LLC in Psychopharmacology
- Vol. 184 (3-4), 314-327
- https://doi.org/10.1007/s00213-005-0076-6
Abstract
Chronic nicotine exposure induces both tolerance and upregulation of [3H]nicotine binding sites in rodent and human brain. However, the mechanism for chronic tolerance is unclear because a direct relationship between tolerance and receptor upregulation is not consistently observed. In the present experiments, the role of β2* nicotinic acetylcholine receptors (nAChRs) on tolerance development and nAChR upregulation was examined following chronic nicotine treatment of β2 wild-type (+/+), heterozygous (+/−), and null mutant (−/−) mice. Saline or nicotine (1, 2, or 4 mg/kg/h) was infused intravenously for 10 days. Locomotor activity and body temperature responses were measured before and after nicotine challenge injection to observe changes in nicotine sensitivity. [3H]Epibatidine binding was then measured in ten brain regions. β2+/+ mice developed dose-dependent tolerance and upregulation of [3H]epibatidine binding sites. In contrast, β2−/− mice, initially less sensitive to acute nicotine's effects, became more sensitive following treatment with the lowest chronic dose (1 mg/kg/h). β2−/− mice treated with 4.0 mg/kg/h nicotine were no longer supersensitive, indicating that tolerance developed at this higher dose. However, these changes in nicotine sensitivity occurred in the absence of any nAChR changes in either low- or high-affinity [3H]epibatidine sites. Responses of β2+/− mice were intermediate between wild-type and mutant mice. Upregulation of nAChRs in vivo requires the presence of the β2 subunit. Changes in nicotine sensitivity occurred both in the presence (β2+/+) and absence (β2−/−) of β2* nAChRs and suggest that mechanisms involving both β2* and non-β2* nAChR subtypes modulate adaptation to chronic nicotine exposure.Keywords
This publication has 52 references indexed in Scilit:
- Subsets of acetylcholine-stimulated 86Rb+ efflux and [125I]-epibatidine binding sites in C57BL/6 mouse brain are differentially affected by chronic nicotine treatmentNeuropharmacology, 2004
- Null mutant analysis of responses to nicotine: Deletion of β2 nicotinic acetylcholine receptor subunit but not α7 subunit reduces sensitivity to nicotine-induced locomotor depression and hypothermiaNicotine & Tobacco Research, 2004
- Differential Regulation of Nicotinic Acetylcholine Receptors in PC12 Cells by Nicotine and Nerve Growth FactorMolecular Pharmacology, 2003
- Chronic nicotine administration does not increase nicotinic receptors labeled by [125I]epibatidine in adrenal gland, superior cervical ganglia, pineal or retinaJournal of Neurochemistry, 2003
- Chronic tolerance to nicotine in humans and its relationship to tobacco dependenceNicotine & Tobacco Research, 2002
- Nicotinic-agonist stimulated 86Rb+ efflux and [3H]epibatidine binding of mice differing in β2 genotypeNeuropharmacology, 2000
- Identification of a novel nicotinic binding site in mouse brain using [125I]‐epibatidineBritish Journal of Pharmacology, 2000
- The paradox of nicotinic acetylcholine receptor upregulation by nicotineTrends in Pharmacological Sciences, 1990
- Evidence that Tobacco Smoking Increases the Density of (−)‐[3H]Nicotine Binding Sites in Human BrainJournal of Neurochemistry, 1988
- Acute and chronic tolerance to nicotine measured by activity in ratsPsychopharmacology, 1973