While both epinephrine and norepinephrine share a similar name and chemical structure, there are some definite differences in the way these neurotransmitters affect the body. Because of their stimulating effects, both hormones can be used as medications, particularly norepinephrine, which is used to enhance mood in those who are severely depressed.
Also known as adrenaline, epinephrine is a hormone and neurotransmitter transferred by the nervous system that creates a fight-or-flight response in the body. Present naturally in the adrenal glands, epinephrine raises the heart rate, constricts blood vessels, dilates pupils and suppresses the immune system.
Norepinephrine is a neurotransmitter and hormone that also is part of the fight-or-flight response in the body. When norepinephrine is released in the body, it raises the heart rate, which causes glucose to be released as energy and blood to flow to the muscles.
Epinephrine and norepinephrine have many similarities: they are both sympathomimetic agents that are similar in chemical structure. Both hormones are produced in the medulla and are released by the adrenal glands. They share many similarities in the actions caused, as both have arousing effects on the body, such as increased heart rate.
Differences: Blood Vessels
When a fight-or-flight response is triggered, the medulla releases 80 percent epinephrine and 20 percent norepinephrine. The norepinephrine causes almost all blood vessels in the body to dilate while the epinephrine restricts smaller blood vessels in the liver and kidneys. Therefore, the body's response in the blood vessels differs slightly.
Unlike epinephrine, norepinephrine is a psychoactive drug that creates a reaction in the brain. Because of this norepinephrine is often included in medications to treat depression. When given in combination with serotonin, another neurotransmitter, norepinephrine can positively affect both mood and behavior.