Three types of galanin receptor (GalR1, GalR2, GalR3) have been cloned to date, and identified to be G-protein coupled receptors. These three galanin receptors show differences in their amino acids sequences, pharmacological properties, as well as in the second messenger system. Activation of GalR1/3 induces inhibition on adenylyl cyclase and to activate K⁺ channels, while activation of GalR2 leads to the stimulation of phospholipase C and intracellular Ca²⁺ mobilization. The distribution of the three galanin receptors in human, rats and mice have been investigated by Northern blot, RT-PCR and in situ hybridization. The different distribution of the galanin receptor indicates that galanin participates a broad range of physiological activities.