Nicotine is an amine (one of a group of compounds that contain nitrogen).1 Nicotine binds to receptors (known as “nicotine acetylcholine receptors”, abbreviated as nAChRs) which are located on the smoker’s muscles and throughout the brain.2 Nicotine stimulates receptors to start a reaction that results in further release of neurotransmitters (chemical messengers that move between nerves, muscles or glands to affect many bodily functions, mood, and behaviour).2, 3
The nicotine receptors that are located in the brain are composed of five subunits arranged around a central space.2 These subunits vary in the way they respond to nicotine and affect the transfer of electrical impulses so that each can produce a variety of responses to nicotine at different rates and concentrations.4 Animal research suggests that the α4β2 receptor subtype is the main receptor affecting nicotine dependence as eliminating the β2 subunit stops the behavioural responses to nicotine.5 Mutations to the α4 subunit changes the sensitivity to nicotine.6 At low doses, nicotine can stimulate central and peripheral systems resulting in, among other effects, an increase in heart rate or blood pressure.4 However, at high doses, nicotine can block nAChrs, resulting in low blood pressure and changes in the body’s capacity to release adrenaline .7
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1. Benowitz NL. Pharmacology of nicotine: Addiction, smoking-induced disease, and therapeutics. Annual Review of Pharmacology and Toxicology, 2009; 49:57–71. Available from: https://www.ncbi.nlm.nih.gov/pubmed/18834313
2. Advocat C, Comaty J, and Julien R, Julien’s primer of drug action. 13th ed New York: Worth Publishers; 2014. Available from: http://www.ncbi.nlm.nih.gov/nlmcatalog/101666863.
3. McKim W and Hancock S, Drugs and behaviour: An introduction to behavioural pharamacology. 7th ed New York: Pearson; 2013.
4. Benowitz N. Clinical pharmacology of nicotine: Implications for understanding, preventing, and teaching tobacco addiction. Clinical Pharmacology & Therapeutics, 2008; 83:531–41. Available from: https://www.ncbi.nlm.nih.gov/pubmed/18305452
5. Picciotto M, Zoli M, Rimondini R, Lean C, Marubio L, et al. Acteylcholine receptors containing the beta2 subunit are involved in the reinforcing properties of nicotine. Nature, 1998; 391:173–7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/9428762
6. Tapper A, CKinney S, Nashmi R, Schwarz J, Deshpande P, et al. Nicotine activation of alpha4* receptors: Sufficient reward, tolerance, and sensitization. Science, 2005; (306):1029–32. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15528443
7. Zevin S, Gourlay SG, and Benowitz NL. Clinical pharmacology of nicotine. Clinics in Dermatology, 1998; 16(5):557–64. Available from: https://www.ncbi.nlm.nih.gov/pubmed/9787965