Dopamine
Dopamine (C6H3(OH)2-CH2-CH2-NH2) is a catecholamine neurotransmitter in the brain.
It can also be supplied as a sympathomimetic drug, i.e. a drug which acts on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure.
Dopamine in the basal ganglia plays a critical role in the way our brain controls our movements. Thus, shortage of dopamine is a cause of Parkinson's disease, in which a person loses the ability to execute smooth, controlled movements.
In the frontal lobes, dopamine plays a role in controlling the flow of information from other areas of the brain. Dopamine disorders in the frontal lobes can cause incoherent thought and even schizophrenia. One of the most effective treatments for schizophrenia is the use of antipsychotic drugs which act as antagonists at dopamine D2 receptors. Shortage of dopamine in the frontal lobes may lead to poor memory.
Dopamine also acts in the limbic system, which controls our emotions. Overabundance of dopamine in the limbic system is believed to cause paranoia.
In addition, dopamine is involved in the chemistry of pleasure. Release of dopamine into that part of the limbic system known as the "pleasure center" (an area just below the thalamus) causes pleasure. Although meant to reward vital activities such as eating and sex, this same mechanism is responsible for the craving connected with addiction to drugs, cocaine for example.
Dopamine is also a hormone released by the hypothalamus. Its main function is to inhibit the release of prolactin from the anterior lobe of the pituitary.
