Nicotine
Nicotine is a chemical substance found in the tobacco plant and its products, including cigarettes, cigars, pipe tobacco, and smokeless tobacco (such as chewing tobacco and snuff). People who smoke cigarettes or use tobacco in other ways can become addicted to the nicotine contained in these products.
Nicotine can occur in two forms. The active form, called L- nicotine, is found in tobacco plants of the genus Nicotiana. These plants belong to the nightshade family (Solanaceae). Nicotiana plants, especially Nicotiana tabacum, were grown for their leaves in South America before the arrival of Christopher Columbus. The inactive form of nicotine, D-nicotine, is not present in tobacco leaves. Instead, a small amount forms when tobacco is burned during smoking. In addition to tobacco plants, small amounts of nicotine are found in foods of the nightshade family, such as tomatoes and eggplants. Nicotine that has been extracted from tobacco leaves is widely used as an insecticide.
The Effects of Nicotine
Nicotine acts in complex ways in the human body. Its effects depend on the amount of the dose, how the dose is taken (for example, by mouth or by injection), the time over which the dose is given, and the individual's history of exposure to nicotine. In high doses, nicotine produces nausea, vomiting, convulsions, muscle paralysis, coma, and circulatory collapse, and causes a person to stop breathing. These severe effects can occur if a person accidentally absorbs an insecticide that contains nicotine or takes an overdose of nicotine.
Nicotine's effects are very different in the smaller amounts found in tobacco products. Taking nicotine by smoking a cigarette or other tobacco products can speed up heart rate and blood pressure; increase the force of contraction of the heart; constrict (narrow) blood vessels in the skin, producing cool, pale skin; constrict blood vessels in the heart; relax the skeletal muscles; increase body metabolic rate; and release hormones such as epinephrine (adrenaline), norepinephrine, and cortisol into the bloodstream.
In the brain, nicotine produces effects partly by enhancing the release of neurotransmitters (brain chemicals) that carry information from one neuron (brain cell) to another. Nicotine enhances the release of the following brain chemicals:
- dopamine, which can produce pleasure
- norepinephrine, which can suppress appetite
- acetylcholine, which can produce arousal
- serotonin, which can reduce anxiety
- beta endorphin, which can reduce pain
Because nicotine produces these desirable effects, people who use tobacco products want to do so repeatedly. As a result, people often become addicted to nicotine.
Addiction: Concepts and Definitions; Adolescents, Drug and Alcohol Use; Brain Chemistry; Nicotine Withdrawal; Tobacco: Dependence; Tobacco: Medical Complications; Tobacco: Policies, Laws, and Regulations; Tobacco: Smokeless; Tobacco Treatment: an Overview; Tobacco Treatment: Behavioral Approaches; Tobacco Treatment: Medications; Tolerance and Physical Dependence.
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