Noradrenaline, or norepinephrine, is a neurotransmitter which is produced and released by the neurons of the peripheral sympathetic nervous system. It is responsible for the adrenergic neurotransmission at nerve endings in the heart, muscle, and in many glands, directly increasing the heart rate and blood flow to skeletal muscle and triggering the release of glucose from energy stores.
Noradrenaline is synthesized from dopamine by dopamine ß-hydroxylase and is released from the adrenal medulla into the blood as a hormone. Tyrosine, an amino acid present in body fluids, is taken up into the adrenergic nerve terminal where it is acted upon by an enzyme, tyrosine hydroxylase, to form DOPA; this is converted to dopamine and in turn to noradrenaline. The neurotransmitter is stored in small vesicles, awaiting release.
Noradrenaline is also an important transmitter in many parts of the central nervous system, where it is involved in arousal, blood pressure regulation, and mood. The noradrenergic neurons in the brain form a neurotransmitter system, which exerts effects on large areas of the brain. The effects are alertness and arousal, and influences on the reward system.