Nicotine itself is not addictive, but it is responsible for releasing dopamine, a neurotransmitter associated with pleasure and reinforcements in the brain, thus inducing addictive tendencies in humans. Nicotine is a chemical found in tobacco leaf, the main ingredient in cigarettes and is said to cause addiction and disease in cigarette smokers, (World Health Organization (WHO)).
Nicotine mimics the activities of acetylcholine, a naturally occurring neurotransmitter in the central nervous system and the nerve-muscle junction of skeletal muscles. Acetylcholine is responsible for excitability, which causes increase heart rate, alertness, and reaction times, (Psychopharmacology (Berl). 1989; 97(2):257-61.). Because acetylcholine and nicotine are chemically similar, they trigger the same cholinergic receptors in the brain. The nicotine-acetylcholine receptors consist of nerve endings that release dopamine when coupled or bind with nicotine or acetylcholine. Receptors are like cups having the exact dimensions that will fit a neurotransmitter molecule, such as acetylcholine.
The cup itself is lined with nerve endings (tips of neurons). It is these nerve endings that release dopamine when the neurotransmitter acetylcholine binds with the cup-like acetylcholine receptors (cholinergic receptors). A reinforcing and reward phenomenon of dopamine develops because the dopamine that is released from the nerve endings initiates a feeling of pleasure in the individual’s brain. The reinforcement mechanism is initiated when the brain becomes addicted to the pleasure caused by the dopamine that is released from the cholinergic receptors. This means that the brain is constantly seeking to be pleasured. So, what will happen in the case of cigarette smokers is that they will continue to smoke cigarettes so the nicotine from the cigarette can induce the release of dopamine in the brain, causing them to feel happy every time they smoke a cigarette, (Nature Reviews Neuroscience 7, 967-975 (December 2006)).
The first time cigarette smokers smoked cigarettes there were only a few cholinergic receptors available because the natural action of acetylcholine only needs the normal amount of receptors provided by nature to do its job. However, the increase concentration of nicotine available caused 電子煙 the normal amounts of cholinergic receptors to become desensitized to the presence of the increased number of nicotine in the cholinergic receptors. This desensitization causes the production or growth and development of more cholinergic receptors. These extra cholinergic receptors will soon become desensitized from the excess nicotine available. Such processes occur until equilibrium is reached. Equilibrium is reached when cigarette smokers decide on the amount of cigarettes they will consume or smoke in a given day. At this time, a fixed amount of receptors will be available for the addiction to continue. Smokers will normally say they smoke one or two packs per day. They said so because of the amount of receptors available to accommodate two packs of cigarettes in a day.
A detrimental effect of all this is the fact that such large amounts of cholinergic receptors are now available and hungry for nicotine. So, they can stimulate dopamine to pleasure the cigarette smoker. This is the reason why cigarette smokers have a very difficult time quitting. The best approach therefore for a cigarette smoker to use in quitting is to gradually cut back on the amount of cigarettes smoked in a given time interval.
In addition to the dopamine-inducing effect of nicotine, is the speeding-up of the heart rate by nicotine every time a cigarette is smoked. From a medical perspective, constantly having an artificial increase in heart rate isn’t a great idea either. For one thing, a constant increase in heart rate by drugs such as nicotine can cause heart disease, (WHO).
According to the World Health Organization, tobacco use leads to diseases affecting the heart and lungs, such as heart attacks, strokes, chronic obstructive pulmonary disease (COPD), emphysema, and cancer. Most cigarette induced cancers are lung cancer, cancers of the larynx, mouth, and pancreas. Cigarette smoke also causes myocardial infarctions, peripheral vascular disease and hypertension. The World Health Organization estimates that tobacco is responsible for about 5.4 million deaths in 2004 and about 100 million deaths during the 20th century.
In addition to its addictive effects on the central nervous system, cigarette smoke contains a multitude of cancer-causing agents. They work by binding to DNA causing many genetic mutations. Nicotine could be the main culprit that is doing the binding to DNA causing genetic mutations, which leads to cancer. Nicotine is said to disrupt the natural processes of apoptosis (programmed cell death) by binding to DNA in cells, (National Institute of Health (NIH)). Defective cells consist of junk DNA and other waste materials. When apoptosis is inhibited, natural cell death does not occur; instead, defective cells are allowed to proliferate or grow larger, uncontrollably. This is what happens in cancer and the main reason why cigarette smokers are more susceptible to developing cancers.
When apoptosis is uncontrollably triggered by chemicals, such as nicotine, it causes normal cells to die off. This could possibly be what is happening in the heart tissues of cigarette smokers who suffer from heart disease and could also be what is taking place in the extremities of cigarette smokers, who often complain of excessive coldness in their fingers, arms, toes, and legs, where circulation is lowest.