Epinepherine and Norepinepherine
By: Derek Charlebois

Hormone: Norepinepherine
Sources: Sympathetic postganglionic nerves (primary), Adrenal Medulla (secondary)
Target receptors: alpha (α1 and α2) and beta (β1, β2, and β3) adrenergic receptors
Receptor Affinity: Greater affinity for alpha then beta-receptors. Greater affinity than E for alpha-receptors.

Norepinephrine

Hormone: Epinepherine
Sources: Adrenal Medulla
Target receptors: alpha (α1 and α2) and beta (β1, β2, and β3) adrenergic receptors Receptor Affinity: Greater affinity for beta than alpha-receptors. Greater affinity than NE for beta-receptors.

Epinephrine

The body strives to maintain homeostasis. During stress, such as exercise, the sympathetic division of the autonomic nervous system is activated in an attempt to reestablish homeostasis. Exercise stimulates an increased delivery of nutrients (glucose, oxygen, etc.) to and removal of waste products (CO2) out of the working muscles. These demands are meet by increasing heart rate, oxygen consumption, mobilizing fuels, and redistributing blood flow. Epinepherine (E) and Norepinepherine (NE) are two of the three catecholamines (Dopamine being the third). E and NE play very important roles in exercise. This article will give a basic overview of their actions during exercise.

The sympathetic nerves are activated early on in exercise and at low exercise intensities. The sympathetic nervous system’s postganglion neurons release NE as their neurotransmitter. When large amounts of NE are produced, such as during exercise, it can “spillover” into the blood and act on receptors throughout the body. This NE “spillover” occurs at above 70% VO2max [1]. E, which is released by the adrenal medulla, acts later in exercise and at high exercise intensities. E is released at above 80-90% VO2max [1].

Actions of Adrenergic Receptors

Biological Function	α1	α2	β1	β2	β3
Amylase Secretion				X
Bronchodilation				X
Heart Rate			X
Heart Contractility	X
Glycogenolysis, Liver	X		X	X
Glycogenolysis, Muscle	X		X	X
Glycolysis	X			X
Gluconeogensis	X
Insulin Secretion				X
Insulin Secretion (Inhibitory)		X
Lipolysis, Adipose Tissue			X	X	X
Lipolysis, Adipose Tissue (Inhibitory)	X
Lipolysis, Muscle				X
NE Release (Inhibitory)		X
Nutrient Uptake (amino acids, lactate)	X
Oxidative Metabolism				X
Piloerection	X
Platelet Aggregation		X
Renin Release			X
Salivation	X
Sweating	X
Vasoconstriction	X	X
Vasodilation				X

Adapted from Table 3.3 in Borer (2003). Exercise Endrocrinology

As shown in the table above, NE and E have a lot of actions in the body. Understanding what NE and E do in the body will allow you to understand how the body responds to stress and exercise as well as their effects on metabolism.

Derek “The Beast” Charlebois is an ACE certified personal trainer, competitive bodybuilder, and holds a Bachelor’s degree in Exercise Science from The University of Michigan. Derek is the Promotions Coordinator/R&D at Scivation/Primaforce and is involved in coordinating promotions, research and development, advertising, and marketing. Derek is an accomplished author with articles on such websites as Bodybuilding.com, Bulknutrition.com, the online magazine StrengthAndScience.com, and contributed to the book Game Over: The Final Showtime Cut Diet You’ll Ever Need! Derek is available for online personal training. His website is www.beastpersonaltraining.com.

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