Catecholamines

Catecholamines are chemical compounds derived from the amino acid tyrosine. Some of them are biogenic amines.

Catecholamines are water soluble and are 50% bound to plasma proteins, so circulate in the bloodstream.

The most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine. They are produced mainly from the adrenal medulla and the postganglionic fibers of the sympathetic nervous system. Adrenaline acts as a neurotransmitter in the central nervous system and as a hormone in the blood circulation. Noradrenaline is primarily a neurotransmitter of the peripheral sympathetic nervous system but is also present in the blood (mostly through "spillover" from the synapses of the sympathetic system).

High catecholamine levels in blood are associated with stress, which can be induced from psychological reaction or environmental stressors such as elevated sound levels or intense light. Catecholamines cause general physiological changes that prepare the body for physical activity (fight-or-flight response). Some typical effects are increases in heart rate, blood pressure, and blood glucose levels. Some drugs, like tolcapone (a central COMT-inhibitor), raise the levels of all the catecholamines.

Catecholamines have the distinct structure of a benzene ring with two hydroxyl groups, an intermediate ethyl chain and a terminal amine group. They have a half-life of approximately a few minutes when circulating in the blood.