Summary
Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and Duboisia hopwoodii) and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits (nAChRα9 and nAChRα10) where it acts as a receptor antagonist. Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. Nicotine is also present at ppb-concentrations in edible plants in the family Solanaceae, including potatoes, tomatoes, and eggplants, though sources disagree on whether this has any biological significance to human consumers. It functions as an antiherbivore toxin; consequently, nicotine was widely used as an insecticide in the past, and neonicotinoids (structurally similar to nicotine), such as imidacloprid, are some of the most effective and widely used insecticides. Nicotine is highly addictive. Slow-release forms (gums and patches, when used correctly) are less addictive and aid in quitting. Animal research suggests that monoamine oxidase inhibitors present in tobacco smoke may enhance nicotine's addictive properties. An average cigarette yields about 2 mg of absorbed nicotine. The estimated lower dose limit for fatal outcomes is 500–1,000 mg of ingested nicotine for an adult (6.5–13 mg/kg). Nicotine addiction involves drug-reinforced behavior, compulsive use, and relapse following abstinence. Nicotine dependence involves tolerance, sensitization, physical dependence, psychological dependence, and can cause distress. Nicotine withdrawal symptoms include depressed mood, stress, anxiety, irritability, difficulty concentrating, and sleep disturbances. Mild nicotine withdrawal symptoms are measurable in unrestricted smokers, who experience normal moods only as their blood nicotine levels peak, with each cigarette. On quitting, withdrawal symptoms worsen sharply, then gradually improve to a normal state.
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Tobacco
Tobacco is the common name of several plants in the genus Nicotiana of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the chief commercial crop is N. tabacum. The more potent variant N. rustica is also used in some countries. Dried tobacco leaves are mainly used for smoking in cigarettes and cigars, as well as pipes and shishas. They can also be consumed as snuff, chewing tobacco, dipping tobacco, and snus.
Dopamine
Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals.
Stimulant
Stimulants (also known as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase the activity of the central nervous system and the body, drugs that are pleasurable and invigorating, or drugs that have sympathomimetic effects. Stimulants are widely used throughout the world as prescription medicines as well as without a prescription (either legally or illicitly) as performance-enhancing or recreational drugs.
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