What Is Norepinephrine?

Understanding this neurotransmitter

Norepinephrine (NE), also called noradrenaline, is a chemical in your body that acts primarily as a neurotransmitter in your nervous system, but can also act as a hormone in the body. It plays a key role in many important functions.

MRI of the brain
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Norepinephrine Functions

Norepinephrine is classified as an excitatory neurotransmitter, which means it stimulates activity in the brain, boosting the function of different cells to keep your brain and body running efficiently.

NE is involved in regulating:

  • Heart rate and blood pressure
  • Blood flow to skeletal muscles
  • Contraction of skeletal muscles
  • Releasing glucose for energy
  • The "fight or flight" response to threats
  • Some aspects of the immune system
  • Inflammation
  • Alertness
  • Memory
  • Arousal or interest
  • Mood
  • The body's response to pain

As both a neurotransmitter and a hormone, NE plays a role in the function of numerous organs throughout your body, including:

  • Eyes
  • Salivary glands
  • Adrenal glands
  • Lungs
  • Liver
  • Gallbladder
  • Stomach
  • Intestines
  • Kidneys
  • Bladder
  • Reproductive organs
  • Skin

Doctors don't generally test norepinephrine levels, so they diagnose NE dysregulation based on symptoms. Be sure you tell them about all of your symptoms so you can work together to find the best treatments.

Low Norepinephrine Activity

When doctors talk about low norepinephrine activity, they don't necessarily mean the amount in your body is abnormally low. Often, in conditions linked to low NE activity, they don't know whether the level itself is the problem. It may be that your body doesn't use it efficiently. It may be a problem with NE receptors, which are basically chemical connecting points on brain and nerve cells that trigger activity.

No matter the specific mechanism(s) involved in low NE activity, the symptoms and treatment remain the same.

Symptoms

Symptoms of low NE activity include:

  • Loss of alertness
  • Memory problems
  • Depression
  • Lack of arousal and interest
  • Foggy brained
  • Fatigued
  • Unmotivated

Associated Conditions

Some of the major conditions linked to low NE activity are:

So far, doctors don't know what leads to low norepinephrine activity in these conditions.

Treatment

Several kinds of treatments can help you boost your NE activity. Common medications that raise norepinephrine levels are:

Other things that raise norepinephrine include:

  • Sleep
  • Exercise
  • Meeting goals
  • Love
  • Aggression

In hypotension, doctors may inject norepinephrine into the bloodstream to raise the blood pressure.

High Norepinephrine Activity

A somewhat high NE activity level makes you happy, and a really high level makes you euphoric. Many recreational drugs get people "high" by increasing levels of norepinephrine (and the related neurotransmitter dopamine). Long-term elevated levels are linked to numerous conditions and symptoms.

Symptoms

Symptoms of high NE activity can be:

  • Worry, anxiety, irritability, racing thoughts
  • Insomnia
  • Fear of crowds
  • Claustrophobia
  • Restless sleep
  • Muscle tension or cramps
  • Impaired concentration

You're probably familiar with the feeling of an "adrenaline rush" when something bad happens or you're startled. That's part of the fight or flight response, in which NE plays a key role.

Fight or Flight

When your brain perceives danger, your sympathetic nervous system triggers a complex response designed to make you able to deal with the threat by running away or physically defending yourself. This is called the fight or flight response.

NE and its cousin, epinephrine (also called adrenaline), are key parts of this response. Along with numerous other hormones, they flood your bloodstream, and that means:

  • Multiple processes to speed up
  • Muscles tense
  • Your brain becomes hyper-focused on the big picture and pays less attention to small tasks
  • Heart rate and blood pressure go up
  • Pupils dilate
  • More blood goes to major muscle groups
  • Blood sugar levels increase
  • More oxygen flows to the lungs
  • Digestion and the immune system are treated as non-essential functions and are shut down so more energy can go to emergency functions

Paroxysmal Sympathetic Hyperactivity

When the body is "stuck" in fight or flight mode, it's called paroxysmal sympathetic hyperactivity. This is considered a set of related symptoms and not an actual medical condition; however, paroxysmal sympathetic hyperactivity is a component of numerous conditions.

Symptoms of paroxysmal sympathetic hyperactivity.

  • Rapid heartbeat
  • High blood pressure
  • Heart palpitations
  • Sweating
  • Anxiety
  • Headache
  • Pale skin
  • Low blood sugar levels
  • Weight loss
  • While the exact causes of paroxysmal sympathetic hyperactivity are not known, it is usually linked to brain injury/trauma and injury of the spinal cord.

Associated Conditions

Conditions linked to high NE activity include:

  • Anxiety disorders
  • Pheochromocytoma (a tumor on the adrenal glands)
  • Chronic stress
  • Bipolar disorder (the manic phase)

Treatment

Drugs that dampen NE activity include:

  • Norepinephrine antagonists: Including Catapres (clonidine), Lopressor (metoprolol), and Minipress (prazosin)
  • Beta-blockers: Such as Sectral (acebutolol), Levatol (penbutolol), Inderal (propranolol)

A couple of supplements that can lower NE activity include:

A Word From Verywell

Neurotransmitter balance is a delicate thing and altering it can cause unpleasant side effects. Be sure to talk to your doctor before you try anything that can change your neurotransmitter levels or activity.

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Additional Reading