Epinephrine

Background

Epinephrine (adrenaline) is a major neurotransmitter of the sympathetic nervous system. Epinephrine partially mediates the body’s reaction to stress by elevating heart rate, blood vessel tone, sweating, tremor, and blood pressure. Epinephrine is released primarily from the central region (medulla) of the adrenal gland in response to stressful situations.

Epinephrine interacts with at least five major protein receptors to produce a plethora of biological responses, typically characterized by an elevation of blood pressure and mobilization of energy stores. The major receptor interactions are with the following: α₁ to both constrict blood vessels, resulting in increased vascular resistance, and an elevation of blood pressure and activate sweat glands to promote nervous sweating; α₂ receptors to reduce the release of other catecholamines, such as norepinephrine, but also to constrict blood vessels; β₁receptors to elevate heart rate and renin secretion, both resulting in...