Biology 103
2002 Second Paper
On Serendip

Nicotine is a colorless liquid that smells like tobacco and turns brown when it is burned (2). It is the chemical in tobacco products that interacts with the brain and causes addiction. The use of tobacco products such as cigarettes, chew, or cigars allow for the nicotine to move quickly throughout the body and the brain. Nicotine can be absorbed through the mucosal linings and skin of the nose and mouth, or through inhalation. When inhaled, the nicotine is absorbed by the lungs and moved into the blood stream from which it reaches the brain in less than eight seconds (4).

The effects of nicotine on the human body are diverse. In high concentrations, through the ingestion of some pesticides or the consumption of tobacco products by children, nicotine can cause convulsions, vomiting and death within minutes due to paralysis. However, in smaller doses nicotine has much milder effects. Nicotine has desirable properties such as heightened awareness and increased short term memory. Other aspects of nicotine include heightened breathing, heart-rate, constriction of arteries and pleasure stimulus in the brain.

Nicotine and the Brain

The brain consists of millions of nerve cells that communicate through chemicals called neurotransmitters. Each neurotransmitter has a particular three dimensional shape that allows it to fit into receptors that are located on the surface of nerve cells (4). Nicotine has a chemical structure that very much resembles the chemical structure of the neurotransmitter Acetylcholine. The similarity of the two chemical structures allows nicotine to activate the Cholinergic receptors naturally stimulated by Acetylcholine. These receptors are located not only in the brain, but also in muscles, adrenal glands, the heart and other peripheral nervous systems (1). These receptors are involved in numerous bodily functions such as muscle movement, breathing, heart rate, learning and memory.

The Nicotine, although very similar to Acetylcholine, does not act exactly like the neurotransmitter and consequently causes the systems that it affects to function abnormally. The Nicotine causes a spontaneous release within the brain of other neurotransmitters that affect mood, appetite and memory. Additionally, many systems such as the respiratory and cardiovascular systems are sped up (4). Nicotine causes the pancreas to release glucose, causing smokers to be marginally hyperglycemic.

Another significant interaction between nicotine and the brain is the release of the neurotransmitter dopamine in the nucleus accumbens (1). Dopamine is a neurotransmitter produced in the pleasure center of the brain. Normally this area of the brain serves to reinforce healthy habits, such as producing dopamine when the body is hungry and then receives food. The production of dopamine causes feelings of reward and pleasure (4)).

Recent studies have showed that nicotine selectively damages the brain. Amphetamines, cocaine, and ecstasy and most addictive drugs damage a particular half of the fasciculus retroflexus. The faciculu retroflexus is a bunch of nerve fibers located above the thalamus. It has been discovered that nicotine affects the other half of these fibers. These fibers control emotional control, sexual arousal, REM sleep and seizures (3).

The Addiction

Nicotine is known to be an addictive drug. Less than seven percent of all smokers who attempt to quit are successful (2). While some of the addiction may be attributed to the social and psychological patterns created by using products containing nicotine, there is also vast evidence that the addiction is chemical as well.

Nicotine causes a strengthening of the connections responsible for the production of Dopamine in the ventral tegmental area (VTA) of the brain pleasure or reward center (5). This strengthening results in a release of dopamine. This is the process used by the brain to enforce positive behavior. The Nicotine artificially stimulates this process, thus encouraging repetition of the Nicotine intake (5).

The Nicotine is quickly metabolized and altogether absent from the body in a few hours, causing the acute affects of the Nicotine to be short lived. This quickly dissipated state of effects creates the need for multiple doses of Nicotine throughout the day in order to prolong the effects and fend off withdrawal (4). Multiple dosages of Nicotine creates a tolerance within the body. In order to receive the desirable traits of the nicotine, the body must consistently take in more of the chemical.

The ending of a Nicotine habit induces both a withdrawal syndrome that lasts about a moth, and intense cravings that may last over six months. The withdrawal syndrome includes such symptoms as irritability, attention deficits, sleep disturbances and increased appetite.

More specific data is sought by the scientific community in order trace the exact portion of the brain responsible for the force of nicotine within the brain. Many studies indicate a particular portion of the receptors with which the nicotine interacts as a key componant in the process of nicotine addiction. The Choinergic receptors that the nicotine stimulates are made up of multiple subunits. In one particular study, the beta subunit was isolated and removed from a number of mice. In subsequent experiments, the mice missing the beta subunit did not self- administer nicotine. The mice with the beta subunit in tact did self administer nicotine (1).

Why Does Any of This Matter?

Nicotine addictions are estimated to account for 70 times the deaths in the United States that all other drug dependences combined (5). Approximately one of every six Deaths in the United States is attributed directly or indirectly to smoking (4). The activities associated with nicotine can cause respiratory problems, lung cancer, emphysema, heart problems, and cancers of the oral cavity, pharynx, larynx and esophagus.

Surveys show that around 90 percent of smokers would like to quit. Unfortunately, because of the addictive qualities of nicotine, very few, less than ten percent are successful (3). Nicotine replacement therapies allow for a lower intake of nicotine, without the harsh effects of tobacco forms of nicotine use. There are also non-nicotine therapies that use pills such as bupropion, an anti depressant, to help quiet the withdrawal effects. Lastly, there are behavioral treatments such as clinics, and formal session based counseling that have been developed and are often used in cooperation with one f the chemical supplements (2).

The continual research on the specific interactions between the brain and nicotine has the potential to create a more effective strategy for those who are seeking to stop using nicotine. It may also be possible to discover how nicotine causes the positive effects such as heightened awareness and strengthened short term memory. This could lead to a method to obtain such effects without receiving the undesirable aspects of nicotine use.

References

Sources

1)Connecticut Clearinghouse, Connecticut State rescource center for iinformation on, and help with, alcohol and drugs

2)http://ericcass.uncg.edu , Educational Information Rescources Center at University of North Carolina

3)www.cnn.com,

4)www.nida.nih.gov, National Institute On Drug Abuse informational sight

5)www.howstuffwrks.com


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