NoradrenalinAdrenalin

NoradrenalinAdrenalin refers to the two closely related catecholamine neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline), which are produced in the adrenal medulla and sympathetic neurons. Both compounds share the chemical structure 2-(3,4-dihydroxyphenyl)ethanamine and function as hormones and neurotransmitters that regulate cardiovascular, metabolic, and stress responses.

Norepinephrine is synthesized from the amino acid tyrosine, followed by conversion to L-DOPA, dopamine, and ultimately norepinephrine by dopamine beta-hydroxylase. It is released from sympathetic nerve endings and acts mainly on alpha- and beta-adrenergic receptors in target tissues such as blood vessels, heart, and smooth muscle. Epinephrine is produced from norepinephrine through the action of phenylethanolamine N‑hydroxylase in chromaffin cells of the adrenal medulla. Epinephrine preferentially activates beta-adrenergic receptors and plays a critical role in the fight-or-flight response, raising heart rate, dilating airways, and mobilizing glucose.

Both neurotransmitters are involved in modulating mood, attention, and arousal. Imbalances in their signaling are linked to hypertension, anxiety, depression, and post-traumatic stress disorder. Clinically, synthetic norepinephrine and epinephrine are used as vasopressors, antihypotensive agents, and treatments for allergic reactions, asthma, and cardiac arrest. Antagonists such as alpha and beta blockers target specific receptor subtypes to manage cardiovascular disorders and cerebral vasospasm. The pharmacokinetics of norepinephrine and epinephrine differ: norepinephrine is rapidly metabolized by monoamine oxidase and catechol-O-methyltransferase, whereas epinephrine has a slightly longer half-life due to additional enzymatic pathways.