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Norepinephrine

Explanations > Brain stuff > Brain chemistry > Neurotransmitters > Norepinephrine

Composition | Function | Dysfunction | See also

Norepinephrine (NE), or noradrenaline, is found in the central and autonomic nervous systems. Its adjective is noradrenergic.

Composition

Chemically, Norepinephrine created within Dopamine-filled vesicules, by the action of dopamine beta-hydroxylase. This is different to other neurotransmitters which are created in the terminal button cytoplasm.

Norepinephrine affects many areas of the brain, though the location of the noragenergic cell bodies is limited largely to the medulla and the pons, in particular the locus coeruleus.

Norepinephrine receptors are usually called adrenergic because they are also sensitive to epinephrine.

Monoamine oxidase type A (MAO-A) destroys excess norepinephrine in the terminal button.

Function

Norepinephrine and epinephrine are both strongly related to the fight-or-flight reaction, increasing heart rate, triggering the release of glucose, and increasing blood flow to skeletal muscles.

Adrenergic receptors lead to both excitation and inhibition, though noradrenergic effects are generally exitatory. Alpha-2 receptors are connected with appetite and sexual activity.

General stress activates the locus coeruleus, from which noradrenergic neurons project to many areas around the brain. A key result of this activation is increased attentiveness to the outside world.

Norepinephrine is also released in the sympathetic nervous system, causing the fight-or-flight response around the body.

Norepinephrine is also a hormone which is released into the bloodstream by adrenal medulla. As a drug, it increases blood pressure.

Dysfunction

Norapinephrine and dopamine are both significant in attention.

Drugs

The antagonist fusaric acid inhibits the action of dopamine beta-hydroxylase and hence prevents the creation of conversion of dopamine to norepinephrine.

Mocolobemide blocks MAO-A and hence is a norepinephrine agonist.

Methylphenidate (Ritalin) acts to stimulate production of norapinephrine and dopamine.

Idazoxoan is an agonist, blocking presynaptic noragenergic alpha-2 receptors and thus preventing reuptake.