Dopamine

Dopamine is a neurotransmitter. Many different kinds of animals and humans use it to transmit information. It is used when the brain sends signals to the muscles in the body to make them move. It can make a person feel good. 
Dopamine is an important chemical found in the brain. If the brain does not make enough dopamine, it causes an illness called Parkinson's disease. This can be treated by giving the Parkinson's disease patient a drug called L-Dopa, which the body converts to dopamine. 
Dopamine is a neurotransmitter that plays many important roles in the human brain and body. If you have ADHD, scientists think that you got it from one of your parents' genes. Typically, a number of genes are involved. Many affect the dopamine neurotransmission. It is a chemical which is triggered by the feeling of being in love, or feeling affection. In most cases, it is also activated by nicotine or cocaine. It can also be activated by marijuana. Many scientist have proven this in the past decade.