C10H14N2. An alkaloid derived from pyridine, found in the leaves of the tobacco plant. It is a poisonous and addictive material, usually indulged in for its relaxing properties. It is also used as an insecticide.
Nicotine constitutes 0.3 to 5% of the tobacco plant by dry weight, with biosynthesis taking place in the roots, and accumulates in the leaves.Chemistry
Nicotine is a hygroscopic, oily liquid that is miscible with water in its base form. Because of this, most nicotine is burned when a cigarette is smoked;
Pharmacology
Pharmacokinetics: As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. The amount of nicotine inhaled with tobacco smoke is a fraction of the amount contained in the tobacco leaves (most of the substance is destroyed by the heat). The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used.
Dynamics
Nicotine acts on the nicotinic acetylcholine receptors. Cotinine is a break-down product of nicotine which remains in the blood for up to 48 hours and can be used as an indicator of a person's exposure to smoke. In high doses, nicotine will cause a blocking of the nicotinic acetylcholine receptor, which is the reason for its toxicity and its effectiveness as an insecticide.
In addition, nicotine increases dopamine levels in the reward circuits of the brain. It is currently believed that nicotine by itself does not inhibit the production of monoamine oxidase (MAO), but that other ingredients in inhaled tobacco smoke are believed to be responsible for this activity.
Toxicology
The LD50 of nicotine is 50 mg/kg for rats and 3 mg/kg for mice.
The carcinogenic properties of nicotine in standalone form, separate from tobacco smoke, have not been evaluated by the IARC, and it has not been assigned to an official carcinogen group. Its teratogenic properties have not yet been adequately researched, and while the likelihood of birth defects caused by nicotine is believed to be very small or nonexistent, nicotine replacement product manufacturers recommend consultation with a physician before using a nicotine patch or nicotine gum while pregnant or nursing. However, nicotine and the increased acetylcholinic activity it causes have been shown to impede apoptosis, which is one of the methods by which the body destroys unwanted cells (programmed cell death). Since apoptosis helps to remove mutated or damaged cells that may eventually become cancerous, the inhibitory actions of nicotine creates a more favourable environment for cancer to develop.
At least one study has concluded that exposure to nicotine alone, not simply as a component of cigarette smoke, could be responsible for some of the neuropathological changes observed in infants dying from Sudden Infant Death Syndrome (SIDS). It was recently argued that the increased level of smoking in schizophrenia may be due to a desire to self-medicate with nicotine.
Therapeutic uses
The primary therapeutic use of nicotine is in treating nicotine dependence (smoking).
Recent studies have indicated that nicotine can be used to help adults suffering from autosomal dominant frontal lobe epilepsy. The same areas that cause seizures in that form of epilepsy are also responsible for processing nicotine in the brain.
Some research has also shown that nicotine can lessen symptoms of mild to moderate ulcerative colitis.
Nicotine and its metabolites are being researched for the treatment of a number of disorders, including ADHD and Parkinson's Disease.
History and name
Nicotine is named after the tobacco plant Nicotiana tabacum, which in turn is named after Jean Nicot, a French ambassador, who sent tobacco and seeds from Portugal to Paris in 1550 and promoted their medicinal use. Nicotine was first isolated from the tobacco plant in 1828 by German chemists, Posselt &
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