Recent analyses of several human populations have identified a number of genetic markers which correlate with aspects of smoking behavior and that correspond to different nAChR subunits. These studies strongly support the contention that genetic differences in receptor subunit structure or expression influence tobacco use. However, it has not been established which of the genetic differences encourage and which discourage tobacco use. Chronic exposure of animals to nicotine, or of humans to tobacco, results in the development of tolerance and dependence. The initial sites of action of nicotine are the nicotinic cholinergic receptors (nAChR), for which the native neurotransmitter is acetylcholine. There are many different types of nAChR in the brain and in the periphery. Nicotine's interaction with these various receptors differs and can lead to different responses to the drug. It is well established that chronic nicotine exposure also changes the number, and perhaps the function, of some nicotinic cholinergic receptors (nAChR). However, chronic nicotine exposure does not affect each nAChR subtype in the same way. Mice will be used as the model organism to examine effects of chronic nicotine treatment. The effects of nicotine in mice are influenced by genotype and mice from which a specific nAChR gene has been deleted (knockout) or mutated (knockin) have been generated. The knockout and knockin mice will be used to investigate some behavioral changes induced by nicotine treatment, primarily tolerance. Furthermore, the effects of chronic nicotine treatment on the expression and function of several different nAChR subtypes will be measured. There are two specific aims. The role of ?4?2*nAChR in modulating response to chronic nicotine will be investigated in Aim 1. ?4?2*- nAChR is the most highly expressed subtype in the brain and chronic nicotine treatment increases the number of these receptors. We plan four types of experiments to study this response in detail a) measure effects in ?4 knockouts, where the gene is completely gone;b) measure the response in mice in which either or both ?4 and ?2 genes have been partially deleted;c) measure response in mice expressing mutations that make these receptors hypersensitive;and d) evaluate the effects of treatment with a drug that interacts selectively with ?4?2-nAChR. The role of the ?5 and ?4 subunits in modulating responses to chronic nicotine will be investigated in Aim 2. ?5 is interesting because it is the nAChR gene that most robustly correlates with tobacco use, while ?4 is interesting because nAChR incorporating this subunit affect nicotine withdrawal and may diminish tolerance development. Response of ?5 and ?4 null mutant and heterozygote mice will be compared to that of wild-type mice. The results of these studies will provide new information on the regulation of the major nicotinic receptor subtype and the contribution of two other subtypes to changes induced by chronic nicotine. The results could also help identify specific behavioral and biochemical responses to chronic nicotine mediated by genes identified as important factors in human smoking.

Public Health Relevance

Chronic use of nicotine or tobacco changes the amount of the specific nicotine-binding molecules (receptors) in both humans and laboratory animals. We will study the responses that chronic nicotine treatment elicits in mice that express fewer or different receptors to determine how these molecular differences affect aspects of nicotine dependence.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
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Neurobiology of Motivated Behavior Study Section (NMB)
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Pollock, Jonathan D
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University of Colorado at Boulder
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McClure-Begley, Tristan D; Grady, Sharon R; Marks, Michael J et al. (2014) Presynaptic GABAB autoreceptor regulation of nicotinic acetylcholine receptor mediated [(3)H]-GABA release from mouse synaptosomes. Biochem Pharmacol 91:87-96
Wageman, Charles R; Marks, Michael J; Grady, Sharon R (2014) Effectiveness of nicotinic agonists as desensitizers at presynaptic *4*2- and *4*5*2-nicotinic acetylcholine receptors. Nicotine Tob Res 16:297-305
O'Neill, Heidi C; Laverty, Duncan C; Patzlaff, Natalie E et al. (2013) Mice expressing the ADNFLE valine 287 leucine mutation of the ýý2 nicotinic acetylcholine receptor subunit display increased sensitivity to acute nicotine administration and altered presynaptic nicotinic receptor function. Pharmacol Biochem Behav 103:603-21
Sala, Mariaelvina; Braida, Daniela; Pucci, Luca et al. (2013) CC4, a dimer of cytisine, is a selective partial agonist at ýý4ýý2/ýý6ýý2 nAChR with improved selectivity for tobacco smoking cessation. Br J Pharmacol 168:835-49
Marks, Michael J (2013) Genetic matters: thirty years of progress using mouse models in nicotinic research. Biochem Pharmacol 86:1105-13
Soll, Lindsey G; Grady, Sharon R; Salminen, Outi et al. (2013) A role for *4(non-*6)* nicotinic acetylcholine receptors in motor behavior. Neuropharmacology 73:19-30
McClure-Begley, Tristan D; Stone, Kathy L; Marks, Michael J et al. (2013) Exploring the nicotinic acetylcholine receptor-associated proteome with iTRAQ and transgenic mice. Genomics Proteomics Bioinformatics 11:207-18
Cohen, B N; Mackey, E D W; Grady, S R et al. (2012) Nicotinic cholinergic mechanisms causing elevated dopamine release and abnormal locomotor behavior. Neuroscience 200:31-41
Gould, Thomas J; Portugal, George S; Andre, Jessica M et al. (2012) The duration of nicotine withdrawal-associated deficits in contextual fear conditioning parallels changes in hippocampal high affinity nicotinic acetylcholine receptor upregulation. Neuropharmacology 62:2118-25
McClure-Begley, Tristan D; Wageman, Charles R; Grady, Sharon R et al. (2012) A novel ýý-conotoxin MII-sensitive nicotinic acetylcholine receptor modulates [(3) H]-GABA release in the superficial layers of the mouse superior colliculus. J Neurochem 122:48-57

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