Teens are “very sensitive to low levels of nicotine,” Krishnan-Sarin reports. “They also get addicted to nicotine a lot faster,” she notes. Vaping as a teen leads to long-term changes in the brain. These often lead to nicotine addiction. Those changes also can prime the brain for addiction problems with other types of drugs.
Nicotine is a highly addictive substance found in tobacco who are addicted to some type of tobacco product, including cigarettes, cigars, chewing tobacco, and snuff.
The nicotinic cholinergic receptor consists of five subunits.6 The mammalian brain expresses nine αsubunits (α2 through α10) and three β subunits (β2through β4). The most abundant receptors are α4β2, α3β4, and α7, the latter of which are homomeric. The α4β2* receptor (the asterisk indicates that other subunits may be present in this receptor) is the principal mediator of nicotine dependence. In mice, disruption of the β2 subunit gene eliminates the behavioral effects of nicotine; reinserting the gene into the ventral tegmental area restores behavioral responses to nicotine.7,8The α4 subunit is an important determinant of sensitivity to nicotine.
This article focuses on nicotine as a determinant of addiction to tobacco and the pharmacologic effects of nicotine that sustain cigarette smoking. Tobacco addiction (like all drug addictions) involves the interplay of pharmacology, learned or conditioned factors, genetics, and social and environmental factors.
Inhalation of smoke from a cigarette distills nicotine from the tobacco in the cigarette. Smoke particles carry the nicotine into the lungs, where it is rapidly absorbed into the pulmonary venous circulation. The nicotine then enters the arterial circulation and moves quickly from the lungs to the brain, where it binds to nicotinic cholinergic receptors (ligand-gated ion channels that normally bind acetylcholine). The binding of nicotine at the interface between two subunits of the receptor opens the channel, thereby allowing the entry of sodium or calcium.5 The entry of these cations into the cell further activates voltage-dependent calcium channels, allowing more calcium to enter. One of the effects of the entry of calcium into a neuron is the release of neurotransmitters.
Together with your doctor, you can talk about all aspects of your addiction, including its severity, and come up with a plan of action that is specific to you that will provide the best chance of recovery. Your doctor may recommend certain prescription medications to help beat nicotine addiction and combat symptoms of withdrawal, but they may also recommend over-the-counter nicotine replacement therapies, such as gum, patches, or lozenges. He or she may also refer you to a mental health specialist for one-on-one counseling.
Nicotine affects the body very quickly, releasing adrenaline and dopamine for a pleasant or calm feeling. In reality, heartbeat and blood pressure have increased. After smoking has ceased, individuals may feel anxious, nervous, or depressed, which is why many people use tobacco many times throughout the day. Eventually, when an addiction becomes strong enough, individuals crave nicotine so much that they may use it habitually throughout the day.
Withdrawal symptoms may appear within hours of the cessation of tobacco use and may last from several days to several weeks, depending on the severity of the addiction. Withdrawal symptoms include:
- Insomnia and restlessness
- Cravings
- Anxiety and nervousness
- Depression
- Dizziness
- Irritability and anger
- Weight gain
- Lack of concentration
- Headaches
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