Catecholamines – Epinephrine & Norepinephrine

Where are catecholamines produced?

In the adrenal medulla:
Epinephrine (~75–80%)
Norepinephrine (~20–25%)

What triggers catecholamine release?

Acute stress ("fight or flight") via the sympathetic nervous system

What are the major effects of epinephrine?

↑ Glycogenolysis and gluconeogenesis
↑ Cardiac output
↑ Lipolysis
↓ Insulin → glucose preserved for brain

What enzyme breaks down catecholamines?

COMT (Catechol-O-methyltransferase)
MAO (Monoamine oxidase)

What are the metabolic breakdown products of catecholamines?

Vanillylmandelic acid (VMA) from epinephrine/norepinephrine
Homovanillic acid (HVA) from dopamine

What is the role of β1 and β2 adrenergic receptors?

β1: ↑ Heart rate, contractility, lipolysis
β2: Vasodilation, bronchodilation, ↑ glycogenolysis/gluconeogenesis

What second messenger system do β1 and β2 receptors use?

↑ cAMP via Gs protein → activates adenylyl cyclase

What is the effect of α1 and α2 adrenergic receptors?

α1: Vasoconstriction via IP3/Ca²⁺
α2: ↓ cAMP → ↓ insulin, ↓ GIT motility