LYCOS RETRIEVER 
Nicotine
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Nicotine is a tertiary amine which is composed of a pyridine and a pyrrolidine ring. Nicotine undergoes a large first pass effect during which the liver metabolizes 80% to 90%; to a smaller extent, the lung ... is able to metabolize nicotine. The major metabolite of nicotine is cotinine; nicotine-1'-N- oxide is a minor metabolite. Cotinine is also extensively metabolized and trans-3'-hydroxycotinine is its a major metabolite. The most abundant metabolite in the mice is trans- 3'-hydroxy-cotinine, accounting for almost 40%, whereas cotinine itself accounts for only about 15% of the dose of nicotine. Cotinine levels in various biological fluids are widely used to estimate intake of nicotine in tobacco users.
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Nicotine is one of two naturally-occurring alkaloids which exhibit their primary effects via autonomic ganglia stimulation. The other alkaloid is lobeline which has many actions similar to those of nicotine but is less potent. Nicotine is a potent ganglionic and central nervous system stimulant, the actions of which are mediated via nicotine-specific receptors. Biphasic actions are observed depending upon the dose administered. The main effect of nicotine in small doses is stimulation of all autonomic ganglia; with larger doses, initial stimulation is followed by blockade of transmission. Biphasic effects are ... evident in the adrenal medulla; discharge of catecholamines occurs with small doses, whereas prevention of catecholamines release is seen with higher doses as a response to splanchnic nerve stimulation.
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Nicotine has various effects on the body. In small doses nicotine serves as a nerve stimulant, entering the bloodstream and promoting the flow of adrenaline, a stimulating hormone. It speeds up the heartbeat and may cause it to become irregular. It ... raises the blood pressure and reduces the appetite, and it may cause nausea and vomiting. Most of the known health risks associated with cigarette smoking, such as damage to the lungs and lung cancer, are caused by other components of cigarettes such as tars and other byproducts of smoking, and by the irritating effects of smoke on the lung tissue. Addiction to smoking is caused by nicotine itself.
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Nicotine has limited carcinogenic effects, inhibiting the body's ability to destroy potentially cancerous cells; ... nicotine does not promote the development of cancer in healthy cells. In addition to the tobacco plant, nicotine is also found in lower quantities in other members of the Solanaceae (nightshade) family, which includes tomato, potato, eggplant (aubergine), and green pepper. Nicotine alkaloids are also found in the leaves of the coca plant.
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Nicotine, one of more than 4,000 chemicals found in the smoke from tobacco products such as cigarettes, cigars, and pipes, is the primary component in tobacco that acts on the brain. Smokeless tobacco products such as snuff and chewing tobacco ... contain many toxins as well as high levels of nicotine. Nicotine, recognized as one of the most frequently used addictive drugs, is a naturally occurring colorless liquid that turns brown when burned and acquires the odor of tobacco when exposed to air. There are many species of tobacco plants; the tabacum species serves as the major source of tobacco products today. Since nicotine was first identified in the early 1800s, it has been studied extensively and shown to have a number of complex and sometimes unpredictable effects on the brain and the body.
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Nicotine withdrawal symptoms include irritability, difficulty concentrating, feelings of depression, difficulty sleeping, increased appetite cravings and headache. These symptoms often start just a few hours after the last cigarette. The first 72 hours of quitting are the hardest, but symptoms may persist for weeks. Smokers have learned that a cigarette will relieve these symptoms in a few moments. But taking nicotine in another form can suppress withdrawal.
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