Can you suppress your craving for cigarettes? Probably ‘NO,’ but why?
Most people consuming cigarettes can’t stop using them due to their addictive nature; this addiction is caused by ‘3-(1-methyl-2-pyrrolidinyl) pyridine, known as nicotine’ one of the thousands of harmful chemicals we inhale with cigarette smoke. These harmful toxins present in cigarette smoke are responsible for various diseases, and nicotine is the one responsible for causing dependency on it.
Nicotine abuse increases levels of dopamine (also known as feel-good neurotransmitters) in the reward, and long-term exposure leads to dependency on it. Nicotine from cigarette smoke reaches the brain within seconds and induces a pleasing effect, which is temporary. This temporary effect soon diminishes, and you reach out for another cigarette and repeat this for that ‘temporary’ pleasure. If someone tries to stop, they might experience withdrawal symptoms, viz., anger, irritability, anxiety, and restlessness. Tobacco abuse is also a significant cause of deaths from cancer and other pulmonary diseases.
How does nicotine affect our brain?
Tobacco smoke consists of around 4000 chemicals, including nicotine; among these, more than 60 are considered carcinogens. The nicotine in smoke travels to the lungs, gets readily absorbed by passive diffusion, and enters the blood circulation, from where it reaches the brain. Peak levels are achieved within 10 seconds of inhalation. Nicotine then binds to the cholinergic receptors, which generally have an affinity to acetylcholine, a neurotransmitter. This nicotine binding to these receptors opens the ion channels, allowing the entry of sodium/calcium ions, which ultimately activates the dopamine neurons to release the neurotransmitter dopamine.
The neurotransmitter dopamine is mainly responsible for nicotine addiction and the withdrawal effect. Nicotine increases dopamine release in the areas targeted by the neurons of the reward circuit. The reward circuit in the brain connects various brain areas/structures that regulate pleasure feelings, ultimately motivating us to repeat the activities or behavior. Hence the reward system is vital for creating motivation which helps the brain in learning and understanding the complex world. This reward circuit comprises dopaminergic neurons (neurons that can synthesize the neurotransmitter dopamine) in the ventral tegmental area (an area in the brain consisting of dopamine synthesizing neurons) of the brain; they project to other regions of the brain that are important in reward processing and releases dopamine when stimulated.
This effect is mediated directly through the nicotinic-cholinergic receptors (nAChR; type of ligand-gated ion channels having affinity to neurotransmitter acetylcholine) present on the dopamine-releasing neurons or indirectly by acting on these receptors on glutamate and GABA neurons, which then modulate the dopamine neurons in the ventral tegmental area. The ultimate effect is an elevated level of dopamine.
All of this creates a pleasing effect due to the activation of the reward circuit. But this effect is very short and dissipates quickly. To maintain such a pleasurable feeling, users reach out for another puff or another cigarette cycle, and this dependency leads to addiction.
Recent studies show that there might be other chemicals that can be addictive other than nicotine. The factors contributing to nicotine addiction may be its pharmacokinetic and dynamics, the physiological response of the user, and availability. Not all cigarette users get addicted to it; around 50% of nicotine addiction is linked to genetic factors.
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- International Agency for Research on Cancer. IARC monographs on the evaluation of carcinogenic risks to humans. Lyon (France): IARC; 2004
- D’Souza MS, Markou A. Neuronal mechanisms underlying development of nicotine dependence: implications for novel smoking-cessation treatments. Addict Sci Clin Pract. 2011 Jul;6(1):4-16. PMID: 22003417; PMCID: PMC3188825.
- NIDA. 2021, April 12. Is nicotine addictive?. Retrieved from https://nida.nih.gov/publications/research-reports/tobacco-nicotine-e-cigarettes/nicotine-addictive on 2022, August 9
- Centers for Disease Control and Prevention (US); National Center for Chronic Disease Prevention and Health Promotion (US); Office on Smoking and Health (US). How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General. Atlanta (GA): Centers for Disease Control and Prevention (US); 2010. 4, Nicotine Addiction: Past and Present. Available from: https://www.ncbi.nlm.nih.gov/books/NBK53018/