Nicotine






CHEMISTRY SOCIAL ISSUE REPORT
Michael Yates 1997

Nicotine

Killer or Wonder Drug ?

Nicotine, one of the most unusual psychoactive drugs known, and the primary pharmacological agent of addiction in cigarettes, triggers powerful physical and psychological reactions in species as diverse as cockroaches and humans.
Nicotine has been proven to boost concentration, improve memory and control body weight, as well as alleviating the symptoms of Alzheimer\'s and Parkinson\'s Disease sufferers. However, research has also established that nicotine adversely affects babies in utero and may explain the link between smoking and problems such as Sudden Infant Death Syndrome and Attention Deficit Disorder.
The hope for the future is that scientists will be able to separate nicotine’s positive properties from its adverse effects, and develop drugs for the treatment of everything from Alzheimer’s disease to weight control .
The chemical’s empirical formula, C10Hl4N2 was determined in the 1840’s, and “nicotine” was synthesized in the 1890’s. Nicotine’s systematic name is 3-(1-methyl-2-pyrrolidinyl) pyridine.
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Together with caffeine and strychnine, nicotine belongs to a group of chemical compounds called pyrrolidine alkaloids. They’re bitter-tasting, often poisonous substances that are made by plants to discourage animals from eating them. Nicotine is a liquid alkaloid which can be obtained from the dried leaves of the tobacco plant, primarily found in a combined form of malate or citrate.
One cigarette contains approximately 1.2 milligrams of nicotine, which, if injected in pure form, is as toxic as hydrogen cyanide, and could kill seven adults. When you smoke, however, you get an extremely diluted dose, about 1 billionth of the nicotine content quoted on the cigarette packet.

Nicotine has an extremely short half life in the body. Within forty minutes it loses about half its strength and the smoker feels the need for another cigarette.
Nicotine has a powerful addicting effect because it is absorbed rapidly into the pulmonary circulation following inhalation from which it passes through the left side of the heart and into the cerebral circulation. It rapidly crosses the blood-brain barrier and binds to specific receptors in various parts of the brain. Stimulation of receptors by nicotine results in the activation of a number of neurohumoral pathways leading to release of acetylcholine, norepinephrine, dopamine, serotonin, vasopressin and various hormones. Nicotine causes the release of the substance b-endorphin, an endogenous peptide that also binds to opiate receptors. This indicates a link between addiction to opiates, such as morphine and heroin, and addiction to nicotine.
Nicotine affects nearly all components of the endocrine and neuroendocrine systems, including catecholamines, serotonin, corticosteroids and pituitary hormones.
Some of these endocrine effects are mediated by actions of nicotine on brain neurotransmitter systems. In addition, nicotine causes skeletal muscle relaxation and has cardiovascular effects.
Nicotine is a powerful substance in controlling brain function. It interacts with specific receptors in brain tissue, and initiates metabolic and electrical activity in the brain.
The individual cells within the brain, the neurons, release a whole array of chemical signals in communication with one another . The most common chemical signal that is used in the brain is a transmitter called glutamate, which stimulates the brain. The production of glutamate requires the brain chemical acetylcholine, and studies have shown that nicotine has similar affects to acetylcholine on the receptors in the brain due to their common dimensions.

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How nicotine acts depends on factors including the amount of nicotine in the body, the time passed since the last cigarette and stress level of the smoker. Nicotine has a stimulating effect, but intake of larger doses can lead to paralysis, vasoconstriction and tachycardia.

Nicotine mimics a chemical that controls heart rate. At blood levels of nicotine achieved by average smokers, stimulation of the central nervous system ultimately results in discharge of sympathetic neurons leading to an increase in blood pressure and heart rate. These changes may be directly or indirectly related to the demonstrated associations of cigarette smoking with heart attacks, worsening of hypertension and stroke.
Researchers realised that nicotine manipulates the mind on many different levels, and consequently conceived that in some way nicotine may even boost concentration, or improve memory.
After smoking cigarettes, smokers perform better on some cognitive tasks than they do when deprived of cigarettes or nicotine. However, nicotine intake does not improve general learning.
Nicotine is a sympatho-mimetic drug, similar to cocaine and amphetamines, stimulating the sympathetic nervous system. Interestingly, scientists have begun to