Stimulant, any of a group of drugs that excite the central nervous system, increase alertness, and alleviate fatigue. Caffeine is perhaps the most socially acceptable and commonly used stimulant. Other stimulants include cocaine and amphetamines, which create intense feelings of euphoria (well-being). Amphetamines, commonly known as pep pills or diet pills, also decrease appetite. Stimulants work by mimicking the fight-or-flight response, in which the hormone epinephrine (also known as adrenaline), is released during stressful situations to produce an increased heart rate and increased blood flow to the muscles. Stimulants produce a similar, but often more powerful, response by increasing levels of the neurotransmitters dopamine and norepinephrine in the brain. Stimulants also appear to act on the limbic system, a group of cell structures in the center of the brain that reward behaviors beneficial to the continuation of the species. These behaviors—sexual intercourse, eating, and drinking—are normally accompanied by positive sensations, which may primarily result from increased levels of dopamine in the limbic system. Stimulants produce an even more potent, euphoric sensation by directly increasing dopamine levels in the limbic system. The appetite-suppressing effect of amphetamines is also thought to derive from the manipulation of this brain reward system: The brain no longer requires food to elevate dopamine levels because the drug has already induced both this elevation and the desired euphoria. For similar reasons, sex drive is often reduced in heavy users of stimulants like cocaine and amphetamine. To achieve these potent feelings of well-being, some stimulants are used for recreational purposes—that is, they are used to produce pleasurable effects rather than for medicinal purposes under a physician’s supervision. But the recreational use of stimulants is dangerous because the drugs can both inspire erratic behavior and produce unpleasant withdrawal symptoms. When the stimulant is eliminated by the body, dopamine levels in the brain fall, producing drug craving, depression, and anxiety. In some cases prolonged use creates a tolerance for the drug, requiring larger and larger doses to produce a comparable effect. And in many instances stimulants are highly addictive (see Drug Dependence).
| TYPES OF STIMULANTS
Cocaine and amphetamines produce closely related biological effects that include excitement, alertness, euphoria, a sense of increased energy, and decreased appetite. Both cocaine and an amphetamine derivative called methamphetamine, commonly known as speed, come in forms that are particularly potent when smoked. They are also highly addictive. Cocaine is sometimes used clinically as a local anesthetic, and amphetamines are commonly prescribed to treat hyperactivity in children, and narcolepsy. Amphetamines were once prescribed as appetite suppressants, but this practice is now discouraged because of negative side effects and the potential for abuse. Nicotine, a highly addictive stimulant found in tobacco, also directly affects dopamine release in the limbic system. The drug, which is quickly absorbed into the bloodstream from the lungs when smoked, causes muscle relaxation, increased heart rate, and release of epinephrine. Withdrawal symptoms include anxiety, anger, restlessness, and insomnia. The basic mechanisms involved in nicotine addiction are nearly identical to those of cocaine and amphetamine addiction. Caffeine, found in coffee, tea, cola drinks, and chocolate, is a highly popular stimulant. Caffeine produces increased mental alertness and reduced fatigue, and increases the heart rate slightly. Caffeine is relatively nontoxic, but clearly has addictive potential. Withdrawal symptoms in heavy users can include severe headache, fatigue, and difficulty in concentrating. Overuse can lead to insomnia, gastrointestinal disturbances, and hypertension. Microsoft ® Encarta ® 2009. © 1993-2008...
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