The catecholamines, dopamine, norepinephrine, and epinephrine, constitute a class of chemical neurotransmitters and hormones that occupy key positions in the regulation of physiological processes and the development of neurological, psychiatric, endocrine, and cardiovascular diseases. Catecholamines, namely dopamine (3,4-dihydrophenylethylamine), norepinephrine (noradrenaline) and epinephrine (adrenaline), act as neurotransmitters or hormones at central and peripheral levels. In addition to being the most abundant of the monoamine neurotransmitters, dopamine is also found in non-neuronal tissues such as the gastrointestinal tract and the kidney, where it participates in the regulation of sodium balance.