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.

Carnitine is a quaternary amine that occurs naturally in most mammalian tissue. It is present in relatively high concentrations in skeletal muscle and heart where it is involved in regulating energy metabolism. It shifts glucose metabolism from glycolysis to glycogen storage and enhances the…

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