Putrescine is a biogenic polyamine and precursor of spermidine. It is formed via decarboxylation of ornithine or by decarboxylation of arginine followed by hydrolysis. Binds to the polyamine modulatory site of the NMDA receptor and potentiates NMDA-induced currents; precursor of spermidine.

NMDA agonist acting at the glycine site; precursor of glycine by serine hydroxymethyltransferase.