Agmatine: an Endogenous Clonidine-Displacing Substance in the Brain

TLDR

Summarize background: context: clonidine binds α2-adrenergic and imidazoline receptors; endogenous ligand may be a clonidine-displacing substance isolated from bovine brain; biosynthetic enzyme present. So background: "Clonidine targets α2‑adrenergic and imidazoline receptors, and an endogenous clonidine‑displacing small molecule was isolated from bovine brain, with its biosynthetic enzyme present in the brain." That covers.

Abstract

Clonidine, an antihypertensive drug, binds to α 2 -adrenergic and imidazoline receptors. The endogenous ligand for imidazoline receptors may be a clonidine-displacing substance, a small molecule isolated from bovine brain. This clonidine-displacing substance was purified and determined by mass spectroscopy to be agmatine (decarboxylated arginine), heretofore not detected in brain. Agmatine binds to α 2 -adrenergic and imidazoline receptors and stimulates release of catecholamines from adrenal chromaffin cells. Its biosynthetic enzyme, arginine decarboxylase, is present in brain. Agmatine, locally synthesized, is an endogenous agonist at imidazoline receptors, a noncatecholamine ligand at α 2 -adrenergic receptors and may act as a neurotransmitter.