Galanin-like peptide is co-localized with alpha-melanocyte stimulating hormone but not with neuropeptide Y in the rat brain.

Galanin-like peptide (GALP), recently isolated from the hypothalamus, is a novel peptide of 60 amino acid residues. GALP is an endogenous ligand of the orphan receptor and shows a high affinity to its specific receptor GalR2. GALP mRNA was shown to be expressed predominantly in the arcuate nucleus (ARC) of the rat hypothalamus, a region considered to be one of the most important feeding-regulating centers in the brain. According to recent reports of morphological and physiological experiments, GALP-containing neurons express leptin receptors and respond to leptin treatment by increasing mRNA expression. However, the relationships between GALP and other feeding-regulating neurons have not yet been proven. In this study, we examined the relationships between GALP- and neuropeptide Y (NPY)- or alpha-melanocyte stimulating hormone ( MSH)-containing neurons by using a dual immunostaining technique. We found that many NPY-immunoreactive fibers were in close apposition with GALP-immunoreactive cell bodies. Furthermore, immunoreactivity for GALP and alpha-MSH was detectable in the same neurons (3.3-11.8%) in the ARC. However, the co-existence of GALP and NPY was never demonstrated. These findings strongly suggest that GALP may participate in the regulation of feeding behavior in harmony with alpha-MSH.