Dopamine is a neurotransmitter that is produced by the brains of many organisms, including humans. Like many neurotransmitters, it has several different functions. It plays a critical role in the function of the central nervous system, and it is also linked with the brain's complex system of motivation and reward. Altered levels of this neurotransmitter in the brain can cause a range of symptoms and problems, ranging from Parkinson's disease to Attention Deficit Disorder (ADD).
The discovery of dopamine as a distinct neurotransmitter was made in 1952 in Sweden. It is a member of the catecholamine family of neurotransmitters, which includes adrenaline and noradrenaline. All of these substances are classified as monoamines, which means that their chemical structure includes an amino group linked with an aromatic ring. The brain biosynthesizes dopamine, taking advantage of precursors produced by or introduced to the body.
In the realm of the central nervous system, dopamine helps the body function smoothly. A decline in this neurotransmitter had been classically linked with Parkinson's Disease, a disease characterized by problems with the central nervous system. Low levels make patients shaky, weak, and confused, and many Parkinson's patients have imperfect control over their bodies.
Dopamine also plays a role in addiction, because it is part of the brain's system of motivation. Some drugs stimulate its production, leading to increased levels and a corresponding high. When the drug exits the system, it leaves behind a sense of depression and a slowdown, which can only be remedied by increasing levels of the neurotransmitter again. The brain quickly learns to seek out drugs that will stimulate production, leading to addiction.
This neurotransmitter is also associated with some psychological conditions, such as psychosis and schizophrenia. It also seems to be involved in attention disorders like ADD, typically in situations where decreased levels make it hard for people to focus.
Because dopamine cannot cross the blood-brain barrier, when it is required in neurological treatment, medical professionals cannot simply give their patients the neurotransmitter directly. Instead, they provide precursors that can cross the barrier, allowing the brain to make it on its own. The neurotransmitter is also sometimes introduced to the bloodstream in treatment for some conditions, since it acts as a diuretic in the body, increasing kidney output. It also raises blood pressure.