Your brain makes dopamine in neurons, or nerve cells, that use it to communicate with other neurons. Each neuron has both transmitter and receptor cites to send and receive dopamine. It is a neurotransmitter. Specialized networks of neurons which are activated by dopamine control purposeful movement, increase alertness and motivation, and suppress appetite and sleep. Medical researchers at MedlinePlus identify dopamine as a catecholamine, a category that includes epinephrine, formerly called adrenalin, and norepinephrine, produced by your adrenal glands.
Availability
Your brain makes most of your dopamine. If you have a medical condition in which your brain loses its ability to manufacture dopamine, you can not benefit from a dopamine shot or pill. The chemical cannot reach your brain from your blood stream. Your blood-brain barrier, a special quality of your brain's circulatory system that protects it from blood-born toxins and other disruptive substances, blocks dopamine. Pharmacologists have discovered that a related chemical, levorotary deoxyphenylalanine, L-DOPA, can be ingested, absorbed into your blood and enter your brain, where it is converted into dopamine.
Anatomy
Only specialized parts of your brain produce dopamine. Neurological researchers at the Lundbeck Institute's CNS Forum describe three major anatomical pathways for dopamine transmission. They lie primarily deep within your midbrain. The first pathway regulates sensory stimuli and movement through connections between brain regions called the substantia nigra and the neostriatum. The second pathway involves parts of the forebrain concerned with cognitive function, emotions and rewards. The third pathway extends from the midbrain to the pituitary gland and regulates major hormone systems.
ADHD Connection
Attention deficit hyperactivity disorder, ADHD, begins in the dopamine neurotransmitter system. ADHD symptoms respond to treatment with stimulants which increase dopamine availability in the brain. This suggests ADHD results from dopamine deficiency in parts of the brain. Recent discovery of genes that regulate dopamine implicate a particular gene mutation in one severe form of ADHD. Childhood lead exposure, fetal oxygen deficits and maternal smoking during pregnancy can inhibit dopamine production and are statistically linked to ADHD.
Disorders
Parkinson's disease, known for uncontrollable shaking and other movement disturbances, arises when cells in the substantia nigra die. Brains of Parkinson's patients contain almost no dopamine. Schizophrenia appears to result from a brain-chemical imbalance that includes excess dopamine in brain centers related to emotions and perceptions.
Medications
Dopamine imbalances respond to replacement of lost dopamine or suppression of excess dopamine production. L-DOPA, which replaces lost dopamine, remains the major medical treatment for Parkinson's disease as of 2010. Dopamine antagonists suppress excess production and relieve many schizophrenic symptoms. Pharmaceutical chemists at California State University list thorazine, reserpine, bromperidal and nemonapride in this class of drugs.
