Increased Nicotinic Acetylcholine Receptor Protein Underlies Chronic Nicotine-Induced Up-Regulation of Nicotinic Agonist Binding Sites in Mouse Brain

Abstract

Chronic nicotine treatment elicits a brain region-selective increase in the number of high-affinity agonist binding sites, a phenomenon termed up-regulation. Nicotine-induced up-regulation of ␣4␤2-nicotinic acetylcholine receptors (nAChRs) in cell cultures results from increased assembly and/or decreased degradation of nAChRs, leading to increased nAChR protein levels. To evaluate whether the increased binding in mouse brain results from an increase in nAChR subunit proteins, C57BL/6 mice were treated with nicotine by chronic intravenous infusion. 125 I]A85380, perhaps because the small ligand penetrated deeply into the sections, whereas the much larger mAbs encountered permeability barriers. Immunoprecipitation of [125 I]epibatidine binding sites with mAb 270 in select regions of nicotine-treated mice was nearly quantitative, although somewhat less so with mAb 299, confirming that the mAbs effectively recognize their targets. The patterns of change measured using immunoprecipitation were comparable with those determined autoradiographically. Thus, increases in ␣4␤2*-nAChR binding sites after chronic nicotine treatment reflect increased nAChR protein.

Treatment for Tobacco Dependence: Effect on Brain Nicotinic Acetylcholine Receptor Density

“…No associations between a 4 b 2 * nAChR densities and treatment type were found, but significant associations were discovered between the extent of a 4 b 2 * nAChR density reduction and the amount of decreased cigarette usage. These results indicate that a 4 b 2 * nAChR density is strongly linked to the number of cigarettes smoked per day, but not to the treatment type being administered, and are consistent with our previous study of untreated smokers (Brody et al, 2013) and other studies linking nicotine (Marks et al, 2011;Yates et al, 1995;Zhang et al, 2002) and cigarette smoke (Mamede et al, 2007;Mukhin et al, 2008;Staley et al, 2006;Wullner et al, 2008) exposure with upregulation of a 4 b 2 * nAChRs in brain regions other than the thalamus. Because education about the biological effects of smoking and quitting smoking are standard parts of smoking-cessation psychotherapy (Fiore et al, 2008), the additional information found here could prove useful in treatment of smokers by letting them know that brain receptor changes found with regular smoking tend toward normalization with smoking reduction and cessation.…”

“…Human postmortem tissue studies show that chronic smokers have increased numbers of a 4 b 2 * nAChRs compared with non-smokers (Benwell et al, 1988;Breese et al, 1997) and that former smokers (41 year abstinent) have nAChR densities similar to nonsmokers (Breese et al, 1997). Many laboratory animal studies also demonstrate upregulation of nAChRs in response to chronic nicotine administration (eg, Marks et al, 2011;Zhang et al, 2002).…”

α-Conotoxins Identify theα3β4* Subtype as the Predominant Nicotinic Acetylcholine Receptor Expressed in Human Adrenal Chromaffin Cells

“…Future experiments are clearly warranted to identify this fifth subunit because auxiliary subunits can play an important role in determining agonist sensitivity and calcium permeability (Gerzanich et al, 1998;Brown et al, 2007;Sciaccaluga et al, 2015). Combined approaches using selective immunoprecipitation, radioligand binding, and immunohistochemistry may be particularly helpful in this regard (Whiteaker et al, 2000;Gotti et al, 2005;Grady et al, 2009;Lomazzo et al, 2010;Marks et al, 2011). Fig.…”

Estrogen Provokes the Depressant Effect of Chronic Nicotine on Vagally Mediated Reflex Chronotropism in Female Rats

“…Moreover, the area postrema is endowed with heteromeric ␣3␤4 nAChRs, which modulate inhibitory GABAergic transmission (Kawa, 2007). The following observations demonstrate that the interaction of nicotine with nAChRs varies depending on receptor, gender, and hormonal profiles: 1) the medullary expression of ␣7 and ␤2 nAChRs is decreased and increased, respectively, by nicotine (Browne et al, 2010), 2) nicotine increases ␣4␤2 nAChR binding sites in mouse brain (Marks et al, 2011), 3) compared with males, nicotine-treated females have higher medullary ␤2 nAChRs (Browne et al, 2010), and 4) estradiol increases ␣7 nAChRs in dorsal raphe and locus coeruleus neurons (Centeno et al, 2006). More studies are obviously needed to determine the relative contributions of central nicotinic receptors in the gender and hormonally dependent nicotine-baroreflex interaction.…”