Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons (nerve cells) to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of the brain, but affect many regions systemically. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain,[4] and many addictive drugs increase dopamine release or block its reuptake into neurons following release.[citation needed] Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory.[citation needed]

In popular culture and media, dopamine is often portrayed as the main chemical of pleasure, but the current opinion in pharmacology is that dopamine instead confers motivational salience;[5][6][7] in other words, dopamine signals the perceived motivational prominence (i.e., the desirability or aversiveness) of an outcome, which in turn propels the organism's behavior toward or away from achieving that outcome.[7][8]

Outside the central nervous system, dopamine functions primarily as a local paracrine messenger. In blood vessels, it inhibits norepinephrine release and acts as a vasodilator (at normal concentrations); in the kidneys, it increases sodium excretion and urine output; in the pancreas, it reduces insulin production; in the digestive system, it reduces gastrointestinal motility and protects intestinal mucosa; and in the immune system, it reduces the activity of lymphocytes. With the exception of the blood vessels, dopamine in each of these peripheral systems is synthesized locally and exerts its effects near the cells that release it.

Cocaine (also cocain) is a strong stimulant drug that is made from coca leaves that is illegal in most countries. Cocaine is usually a white powder. Because it is a stimulant, cocaine gives people energy. It also makes people feel very happy when it is taken. When used this way, cocaine is very addictive. However, cocaine can also be used as a local anesthetic if it is applied topically (onto the skin or gums).[1]

The Inca of Peru were consumers. [2] Cocaine is taken from the leaves of the coca plant of South America. [3] Coca plants are mostly grown in South America, in countries like Brazil or Argentina. When Spanish conquistadors (explorers) discovered coca plants, they sent them back to Europe. People started using cocaine as a medicine, as well as in drinks and food. This was because they did not know how damaging and addictive the drug could be when used.

In America, cocaine was used during surgery, or to treat toothaches. It was also put into drinks. When Coca-Cola was first made in 1885, it got the first part of its name from the "handful of coca leaves" added to the drink for energy. (The caffeine in the drink came from the kola nut, so the name "Coca-Cola" was chosen.) Cocaine was taken out of Coca-Cola completely by the 1920s because of pressure from groups in the United States.