Agmatine

Agmatine ((4-aminobutyl)guanidine, NH2-CH2-CH2-CH2-CH2-NH-C(-NH2)(=NH)) is the decarboxylation product of the amino acid arginine and is an intermediate in polyamine biosynthesis. It is discussed as a putative neurotransmitter. It is synthesized in the brain, stored in synaptic vesicles, accumulated by uptake, released by membrane depolarization, and inactivated by agmatinase. Agmatine binds to α2-adrenergic receptor and imidazoline binding sites, and blocks NMDA receptors and other cation ligand-gated channels. Agmatine inhibits nitric oxide synthase (NOS), and induces the release of some peptide hormones. Treatment with exogenous agmatine exerts neuroprotective effects in animal models of neurotrauma.

The term "agmatine" was coined in 1910 by Albrecht Kossel, the German scientist who first identified the substance in herring sperm.