Dopamine is a metabolic neurotransmitter which is produced in several areas of the brain that include the substantia nigra and the ventral tegmental area. It is the main neurotransmitter in extrapyramidal tracts. High dopamine levels have been linked to aggression.
In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D1, D2, D3, D4 and D5, and their variants. Dopamine is also a neurohormone released by the sympathetic ganglia in the hypothalamus. Its function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.
In neurons, dopamine is packed into vesicles, which are then released into the synapse in response to a presynaptic action potential. When supplied as a medication, dopamine acts on the sympathetic nervous system and produces effects such as increased heart rate and blood pressure.
Dopamine has many functions in the brain, including important roles in behavior and cognition, motor activity, motivation and reward, inhibition of prolactin production, which is involved in lactation, sleep, mood, attention, and learning.