Epinephrine and norepinephrine belong to a group of compounds known as catecholamines. These compounds act as both neurotransmitters, delivering signals between nerve cells, and hormones.
Epinephrine and norepinephrine have similar chemical structures. However, they produce different effects on the body. Both play a role in the regulation of the sympathetic nervous system, which is responsible for the body’s “fight or flight” response.
Another name for epinephrine is adrenaline, and some refer to norepinephrine as noradrenaline.
In this article, we discuss the similarities and differences between epinephrine and norepinephrine, along with their functions and medical uses. We also outline the health effects of having too much or too little of either compound in the body.
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Both epinephrine and norepinephrine are chemical messengers. They function as hormones, as well as neurotransmitters.
As hormones, epinephrine and norepinephrine travel through the bloodstream, along with other hormones that the endocrine and reproductive organs make. They tell organs and tissues to work in different ways.
Neurotransmitters have a similar function. However, they only occur in nerve cells and travel across synapses, which are junctions where two nerve fibers meet. Nerves cells produce neurotransmitters in response to electrical impulses.
The adrenal medulla is the inner portion of the adrenal gland. It regulates and secretes both epinephrine and norepinephrine in response to stress and other imbalances in the body, such as low blood pressure.
What does epinephrine do?
When the brain perceives danger, the amygdala triggers the hypothalamus to activate the autonomic nervous system (ANS).
Signals from the ANS stimulate the adrenal gland to start pumping epinephrine into the bloodstream. People often refer to this surge of epinephrine as an adrenaline rush or the fight or flight response.
Epinephrine activates alpha- and beta-adrenoreceptors in the cells of various body organs and tissues, including:
- the heart
- the lungs
- the muscles
- the blood vessels
The release of epinephrine into the bloodstream brings about several physiological changes, such as:
What does norepinephrine do?
The adrenal medulla produces norepinephrine in response to low blood pressure. Norepinephrine promotes vasoconstriction, which is a narrowing of the blood vessels. This, in turn, increases blood pressure.
Like epinephrine, norepinephrine also stimulates alpha-adrenoreceptors in the cells of the blood vessels. It increases heart rate and blood sugar levels.
Synthetic forms of epinephrine and norepinephrine have several medical uses.
Epinephrine
Doctors prescribe epinephrine to treat severe medical conditions that affect the heart and airways, such as anaphylaxis.
Anaphylaxis is a severe and life threatening allergic reaction that can interfere with a person’s ability to breathe. Epinephrine counters anaphylactic shock by:
- narrowing the blood vessels to increase blood pressure
- increasing heart rate to improve blood flow
- relaxing the muscles and airways, allowing a person to breathe
People at risk of anaphylaxis can carry an epinephrine autoinjector with them at all times.
Doctors may also use epinephrine to treat the following:
- severe asthma attacks
- cardiac arrest
- septic shock
During asthma attacks, doctors use epinephrine in a nebulized or inhaled form, rather than injecting it.
In cases of septic shock, doctors may use epinephrine and norepinephrine at the same time, delivering it via an IV line.
Norepinephrine
Norepinephrine can help raise systolic blood pressure (SBP) in people who have had a heart attack. Systolic blood pressure refers to the pressure that occurs when the heart is contracting and ejecting blood. A heart attack can damage and weaken the heart muscle, resulting in low SBP.
Doctors may also use norepinephrine to treat the following:
- Critical hypotension: This is the medical term for dangerously low blood pressure.
- Septic shock: This is a life threatening condition in which blood pressure drops dangerously low following an infection. Doctors may combine norepinephrine with IV fluids and antibiotics to treat septic shock.
- Pericardial tamponade: This is another life threatening condition in which the heart is unable to fully expand and fill with blood due to fluid in the pericardium, which is the membrane surrounding the heart. Doctors treat it via pericardiocentesis, which removes the excess fluid, as well as norepinephrine.
- Neurogenic shock: This occurs when damage to the nervous system causes difficulty maintaining a stable heart rate, blood pressure, and temperature.
Certain medical conditions can affect the adrenal glands, causing excess production of epinephrine and norepinephrine. Examples include:
- chronic stress
- obesity
- tumors
Symptoms of high levels of epinephrine or norepinephrine can include:
A 2018 review article states that having high levels of norepinephrine can increase a person’s risk of cardiovascular and kidney damage.
An epinephrine overdose can occur in people who use epinephrine injections to treat certain medical conditions. An overdose of injected epinephrine can lead to dangerously high blood pressure, stroke, or even death.
Epinephrine and norepinephrine are similar chemicals that act as both neurotransmitters and hormones in the body. Both substances play an important role in the body’s fight or flight response, and their release into the bloodstream causes increases in blood pressure, heart rate, and blood sugar levels.
Epinephrine acts on the alpha- and beta-adrenoreceptors in the muscles, lungs, heart, and blood vessels. Norepinephrine is a metabolite of dopamine that primarily acts on the alpha-adrenoreceptors in the blood vessels.
Doctors may prescribe epinephrine to treat potentially life threatening conditions, such as anaphylaxis, severe asthma attacks, and cardiac arrest. A doctor may prescribe norepinephrine to raise dangerously low blood pressure following a heart attack, critical hypotension, or septic shock.
Neurotransmitters are chemical messengers in the body. Their job is to transmit signals from nerve cells to target cells. These target cells may be in muscles, glands, or other nerves.
Neurotransmitters are part of the nervous system. They play a crucial role in human development and many bodily functions.
This article explains what neurotransmitters are, what they do, and some different types.
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The nervous system controls the body’s organs and plays a role in nearly all bodily functions. Nerve cells, also known as neurons, and their neurotransmitters play important roles in this system.
Nerve cells fire nerve impulses. They do this by releasing neurotransmitters, also known as the body’s chemical messengers. These chemicals carry signals to other cells.
Neurotransmitters relay their messages by traveling between cells and attaching to specific receptors on target cells.
Each neurotransmitter attaches to a different receptor. For example, dopamine molecules attach to dopamine receptors. When they attach, it triggers an action in the target cells.
After neurotransmitters deliver their messages, the body breaks them down or recycles them.
Experts have identified over 100 neurotransmitters to date and are still discovering more.
Neurotransmitters have different types of actions:
- Excitatory neurotransmitters encourage a target cell to take action.
- Inhibitory neurotransmitters decrease the chances of the target cell taking action. In some cases, these neurotransmitters have a relaxation-like effect.
- Modulatory neurotransmitters can send messages to many neurons at the same time. They also communicate with other neurotransmitters.
Some neurotransmitters can carry out several functions depending on the type of receptor they connect to.
The following sections describe some of the best-known neurotransmitters.
Acetylcholine is an excitatory neurotransmitter with a wide range of roles.
For example, it:
- triggers muscle contractions
- stimulates saliva and sweat production
- controls the heartbeat
It also plays a role in memory, motivation, and attention.
Low levels of acetylcholine link with issues relating to memory and thinking, such as Alzheimer’s disease.
Some Alzheimer’s disease medications help slow the breakdown of acetylcholine in the body. This can help manage some symptoms, such as memory loss.
Having high levels of acetylcholine can cause too much muscle contraction.
This can lead to:
- increased saliva and tears
- muscle weakness and paralysis
- diarrhea
- blurry vision
The nutrient choline, present in many foods, is a building block of acetylcholine. People need choline in their diet to produce enough acetylcholine. However, it is not clear whether consuming more choline can help boost levels of this neurotransmitter.
Choline is present in beef liver, eggs, soybeans, and potatoes. Choline supplements are also available. However, there is not enough evidence to show they help with any health condition. However, taking too much can have adverse effects, such as a fishy body odor, sweating, low blood pressure, and liver damage.
Dopamine is important for:
- memory
- learning
- behavior
- movement control
- regulating blood flow
Many people know dopamine as a pleasure or reward neurotransmitter. The brain releases dopamine during pleasurable activities.
Researchers believe there is a link between dopamine deficiency and Parkinson’s disease.
Drugs that regulate dopamine levels may help treat features of Parkinson’s disease as well as depression, addiction, anxiety, bipolar disorder, and other conditions.
The body needs certain amino acids to produce dopamine. Amino acids are present in protein-rich foods, such as meat, fish, and eggs. However, there is no evidence that suggests eating these foods makes a difference in dopamine levels.
While there are no dopamine supplements, exercise may help boost levels naturally. Research has shown that regular exercise improves dopamine signaling in people with early stage Parkinson’s disease.
Endorphins inhibit pain signals and create a feeling of pleasure. They have links to laughter, love, sex, and appetizing food.
Many people feel better after exercising. One reason for this may be that exercise boosts endorphin levels. Laughter may also cause a release of endorphins, according to research published in The Journal of Neuroscience.
Endorphins may also help manage pain. A review of research published in Current Pain and Headache Reports says that aerobic exercise can help prevent migraine frequency, duration, and intensity.
The Arthritis Foundation recommends exercise for people with fibromyalgia to reduce pain and boost mood.
Epinephrine (also known as adrenaline) plays a role in the body’s “fight-or-flight” response. It is both a hormone and a neurotransmitter.
When a person experiences stress or fear, their body releases epinephrine. This increases heart rate and breathing and gives the muscles a jolt of energy. It also helps the brain make quick decisions.
However, chronic stress can cause the body to release too much epinephrine. Over time, stress can lead to health problems such as decreased immunity, high blood pressure, diabetes, and heart disease, according to the National Institute of Mental Health.
Doctors can use epinephrine to treat some life threatening conditions, including:
Epinephrine’s ability to constrict blood vessels can decrease swelling that results from allergic reactions and asthma attacks. In addition, it can help the heart contract again if it has stopped during cardiac arrest.
Serotonin is an inhibitory neurotransmitter. It helps regulate mood, behavior, sleep, and memory.
Seasonal affective disorder (SAD) causes symptoms of depression in the fall and winter when daylight is less abundant. Research published in Brain suggests there may be a link between SAD and low serotonin levels.
Doctors prescribe selective serotonin reuptake inhibitors (SSRIs) to treat a range of conditions, including:
SSRIs boost serotonin levels by stopping the body from reabsorbing serotonin, leaving more serotonin to pass messages between nerve cells.
Serotonin-norepinephrine reuptake inhibitors (SNRIs) increase serotonin and norepinephrine, another neurotransmitter. SNRIs can help relieve symptoms of depression, anxiety, chronic pain, and fibromyalgia.
Evidence published in the journal Cell indicates that exposure to sunlight may help increase serotonin levels, although people should take care to avoid sunburn.
A precursor to serotonin, 5-hydroxytryptophan, is available as a supplement. Some studies suggest this ingredient may help treat depression and other conditions. However, more research is needed.
People should speak with a doctor before taking this supplement, or any supplement, to treat depression.
Learn more about SSRIs and other antidepressants.
Neurotransmitters contribute to nearly every function in the human body. An appropriate balance of neurotransmitters can help prevent certain health conditions, such as depression, anxiety, and Parkinson’s disease.
There is no proven way to ensure that neurotransmitters are balanced and working correctly. However, consuming a nutritious diet, getting regular exercise, and stress management can help in some cases.
Some people try supplements to boost certain neurotransmitters. In most cases, there is not enough evidence to show they work. Anyone considering using supplements should check first with a doctor. Supplements can interact with medications and may not be safe to use with some health conditions.
Anyone experiencing symptoms that may be due to an imbalance should seek medical advice.