Norepinephrine (NE), also called norepinephrine (NA), is an organic chemical in the catecholamine family that works in the brain and body as a hormone and a neurotransmitter. This substance that is released predominantly from the ends of sympathetic nerve fibers and that acts to increase the force of skeletal muscle contraction, the speed and force of contraction of the heart.
The actions of norepinephrine are vital to the fight or flight response, whereby the body prepares to react to or withdraw from an acute threat.
Norepinephrine is similar to adrenaline. It works by narrowing blood vessels and increasing blood pressure and blood glucose (sugar) levels.
Norepinephrine is structurally classified as a catecholamine, containing a catechol group (a benzene ring with two hydroxyl groups) attached to an amine group (containing nitrogen). The addition of a methyl group to the amino group of norepinephrine results in the formation of epinephrine, the other major mediator of the escape or flight response..
Compared to epinephrine, which is produced and stored primarily in the adrenal glands, norepinephrine is stored in small amounts in the adrenal tissue. Its main storage and release zone are neurons of the sympathetic nervous system (a branch of the autonomic nervous system). Therefore, norepinephrine works primarily as a neurotransmitter with some function as a hormone that is released into the bloodstream from the adrenal glands..
Norepinephrine or noradrenaline transmits information in the form of electrical impulses to different parts of the body. It is released through adrenergic neurons of the Central Nervous System (CNS). It also exerts its function in the Autonomous Nervous System (ANS), generating the activation of our body in situations of anxiety..
Thus, one of the main functions of norepinephrine as a neurotransmitter is the stimulation of adrenaline production in the body, causing an increase in vigilance activity, facilitating attention and improving the ability to react to possible dangerous events..
Also known as one of the stress hormones, norepinephrine is released into the blood after being synthesized by the amino acid called tyrosine through the adrenal glands, located above the kidneys..
Norepinephrine exerts its effects by binding to α and β adrenergic receptors (or adrenoceptors, named for their reaction to adrenal hormones) in different tissues. In blood vessels, it triggers vasoconstriction (narrowing of the blood vessels), which increases blood pressure. Norepinephrine further increases blood pressure as a result of its effects on the heart muscle, which increases the heart's blood production.
Norepinephrine also works to increase blood glucose levels and circulating free fatty acid levels. The substance has also been shown to modulate the function of certain types of immune cells.
Norepinephrine that diffuses from local nerve endings can act on adrenergic receptors at distant sites.
Norepinephrine is used clinically as a means of maintaining blood pressure in certain types of disorders (eg, septic shock or septicemia). It is also used to treat life-threatening low blood pressure (hypotension) that can occur with certain medical conditions or surgical procedures. This drug is often used during CPR (cardiopulmonary resuscitation)..
The Swedish physiologist Ulf von Euler identified norepinephrine in the mid-1940s; received a share of the 1970 Nobel Prize in Physiology or Medicine for his discovery.
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Michael W. King. Biochemistry of neurotransmitters and nerve transmission: catecholamines. Indiana University School of Medicine