<p>Dopamine is a preparation of Dopamine hydrochloride which can stimulate &alpha;, &beta; and dopamine receptors. It is a natural catecholamine formed by the decarboxylation of 3,4-dihydroxyphenylalanine (DOPA). Dopamine is a precursor to norepinephrine in noradrenergic nerves and is also a neurotransmitter in certain areas of the central nervous system, especially in the nigrostriatal tract and in a few peripheral sympathetic nerves. It produces positive chronotropic and inotropic effects on the myocardium, resulting in increased heart rate and cardiac contractility. This is accomplished directly by exerting an agonist action on &beta;-adrenoceptors and indirectly by causing release of norepinephrine from storage sites in sympathetic nerve endings. Dopamine does not cross the blood-brain barrier and so does not activate dopamine receptors in the brain.</p>