Galanin/GALP receptors and CNS homeostatic processes.

Galanin is a 29/30 amino acid peptide neurotransmitter that is widely distributed throughout the central nervous system and periphery. There are three well-characterized G-protein coupled galanin receptors subtypes (GalR1-3). A more recently discovered 60 amino acid galanin-like peptide (GALP) shares amino acid sequence homology with galanin (1-13) in position 9-21 and has high binding affinity for GalR1-3, with highest affinity for GalR3. Considerable evidence has accumulated that implicates both galanin and GALP as playing important roles in regulating food and water intake behavior and related neuroendocrine functions. Pharmacological tools are emerging that will allow dissociation of specific roles for the peptides and their associated receptor subtypes in mediating the homeostatic processes of energy and fluid balance.