What is the difference between adrenaline and noradrenaline? · Grey Matter

Chemically they differ by one methyl group: adrenaline is made from noradrenaline by one more enzymatic step, and both act on the same family of adrenergic receptors.

What is the difference between adrenaline and noradrenaline?

Chemically they differ by one methyl group: adrenaline is made from noradrenaline by one more enzymatic step, and both act on the same family of adrenergic receptors. The difference is where they are released. Noradrenaline is a neurotransmitter, released by sympathetic nerves onto organs and, inside the brain, by the locus coeruleus onto almost every region. Adrenaline is mainly a hormone, released into the blood by the adrenal medulla, and it barely crosses the blood-brain barrier, so the brain's arousal runs on its own noradrenaline while adrenaline acts on the body.