A drug in tobacco which acts as a stimulant and is responsible for dependence on tobacco. After inhalation, the nicotine in tobacco smoke passes rapidly into the bloodstream. The drug acts on the nervous system until broken down by the liver and excreted in the urine.
Nicotine acts primarily on the autonomic nervous system, which controls involuntary body activities such as the heart rate. In habitual smokers, the drug increases the heart rate and narrows the blood vessels, the combined effect of which is to raise blood pressure. Nicotine also stimulates the central nervous system, thereby reducing fatigue, increasing alertness, and improving concentration.Stopping smoking often causes withdrawal symptoms such as headaches and difficulty in concentrating. Nicotine replacement therapy, such as the use of nicotine skin patches and chewing gum, can be effective in aiding withdrawal from nicotine. (See also smoking.)
An alkaloid which is the principal addictive agent in TOBACCO. The small amount of nicotine in a single cigarette is su?cient to stimulate mental and bodily activities. In larger quantities it acts as a depressant or narcotic – habitual smokers may ?nd its e?ect sedating. Nicotine works by stimulating the production of a chemical called DOPAMINE, a neurotransmitter or chemical messenger between nerve cells. Nicotine mimics the action of a neurotransmitter called ACETYLCHOLINE. Nerve cells that produce dopamine have acetylcholine-receptor molecules on their surfaces; when these ‘nicotine-like’ receptors are occupied by acetylcholine molecules, a cell is prompted to produce dopamine. So nicotine itself can arti?cially stimulate dopamine production. Dopamine is part of the neuronal circuitry that plays a part in the body’s perception of pleasure, which is why smoking is enjoyed by many people.
n. a poisonous alkaloid derived from *tobacco, responsible for the dependence of regular smokers on cigarettes. In small doses nicotine has a stimulating effect on the autonomic nervous system, causing in regular smokers such effects as raised blood pressure and pulse rate and impaired appetite. Large doses cause paralysis of the autonomic ganglia. Nicotine replacement therapy (nicotine products formulated as chewing gum, skin patches, nasal sprays, etc.) is used as an aid to stop smoking.
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