Norepinephrine

Norepinephrine

Skeletal formula of noradrenaline
Ball-and-stick model of the zwitterionic form of noradrenaline found in the crystal structure[1]
Clinical data
Other names	NE, NA, Noradrenaline, (R)-(–)-Norepinephrine, l-1-(3,4-Dihydroxyphenyl)-2-aminoethanol 3,4,β-Trihydroxyphenethylamine
Physiological data
Source tissues	locus coeruleus; sympathetic nervous system; adrenal medulla
Target tissues	system-wide
Receptors	α1, α2, β1, β3
Agonists	sympathomimetic drugs, clonidine, isoprenaline
Antagonists	Tricyclic antidepressants, beta blockers, antipsychotics
Precursor	dopamine
Biosynthesis	dopamine β-monooxygenase
Metabolism	MAO-A; COMT
Identifiers
IUPAC name (R)-4-(2-amino-1-hydroxyethyl)benzene-1,2-diol
CAS Number	51-41-2 Y
PubChem CID	439260
IUPHAR/BPS	505
DrugBank	DB00368
ChemSpider	388394
UNII	X4W3ENH1CV
KEGG	C00547
ChEBI	CHEBI:18357
ChEMBL	ChEMBL1437
CompTox Dashboard (EPA)	DTXSID5023378
ECHA InfoCard	100.000.088
Chemical and physical data
Formula	C8H11NO3
Molar mass	169.180 g·mol−1
3D model (JSmol)	Interactive image
SMILES NC[C@H](O)c1cc(O)c(O)cc1
InChI InChI=1S/C8H11NO3/c9-4-8(12)5-1-2-6(10)7(11)3-5/h1-3,8,10-12H,4,9H2/t8-/m0/s1 Key:SFLSHLFXELFNJZ-QMMMGPOBSA-N

Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as a hormone, neurotransmitter and neuromodulator. The name "noradrenaline" (from Latin ad, "near", and ren, "kidney") is more commonly used in the United Kingdom, whereas "norepinephrine" (from Ancient Greek ἐπῐ́ (epí), "upon", and νεφρός (nephrós), "kidney") is usually preferred in the United States.^[2] "Norepinephrine" is also the international nonproprietary name given to the drug.^[3] Regardless of which name is used for the substance itself, parts of the body that produce or are affected by it are referred to as noradrenergic.

The general function of norepinephrine is to mobilize the brain and body for action. Norepinephrine release is lowest during sleep, rises during wakefulness, and reaches much higher levels during situations of stress or danger, in the so-called fight-or-flight response. In the brain, norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention; it also increases restlessness and anxiety. In the rest of the body, norepinephrine increases heart rate and blood pressure, triggers the release of glucose from energy stores, increases blood flow to skeletal muscle, reduces blood flow to the gastrointestinal system, and inhibits voiding of the bladder and gastrointestinal motility.

In the brain, noradrenaline is produced in nuclei that are small yet exert powerful effects on other brain areas. The most important of these nuclei is the locus coeruleus, located in the pons. Outside the brain, norepinephrine is used as a neurotransmitter by sympathetic ganglia located near the spinal cord or in the abdomen, as well as Merkel cells located in the skin. It is also released directly into the bloodstream by the adrenal glands. Regardless of how and where it is released, norepinephrine acts on target cells by binding to and activating adrenergic receptors located on the cell surface.

A variety of medically important drugs work by altering the actions of noradrenaline systems. Noradrenaline itself is widely used as an injectable drug for the treatment of critically low blood pressure. Stimulants often increase, enhance, or otherwise act as agonists of norepinephrine. Drugs such as cocaine and methylphenidate act as reuptake inhibitors of norepinephrine, as do some antidepressants, such as those in the SNRI class. One of the more notable drugs in the stimulant class is amphetamine, which acts as a dopamine and norepinephrine analog, reuptake inhibitor, as well as an agent that increases the amount of global catecholamine signaling throughout the nervous system by reversing transporters in the synapses. Beta blockers, which counter some of the effects of noradrenaline by blocking their receptors, are frequently used to treat glaucoma, migraine, and a range of cardiovascular problems. Alpha blockers, which counter a different set of noradrenaline effects, are used to treat several cardiovascular and psychiatric conditions. Alpha-2 agonists often have a sedating effect and are commonly used as anesthesia enhancers in surgery, as well as in treatment of drug or alcohol dependence. For reasons that are still unclear, some Alpha-2 drugs, such as guanfacine, have also been shown to be effective in the treatment of anxiety disorders and ADHD. Many important psychiatric drugs exert strong effects on noradrenaline systems in the brain, resulting in effects that may be helpful or harmful.