Distribution and Neuronal Networks of Novel GPCR Ligands in Feeding Regulation

Recent studies have shown that a number of novel G-protein coupled receptor (GPCR) ligands localize in brain tissue and perform a range of physiological functions, some of which have been studied and clarified, and others about which less is known. Here, we wish to describe the distribution and localization of GPCR ligands identified thus far and to examine their involvement in neuronal networks, particularly those networks related to feeding regulation. The review analyzes published reports of morphological and physiological data looking mainly at the functional significance of feeding-regulation factors, such as those described by our research group and others, and neuronal interactions among these GPCR ligands in the hypothalamus. Cross-talk among several GPCR ligand-containing neuron types in the hypothalamus plays a role in determining feeding states. We introduce structural and functional characteristics of novel GPCR ligands and summarize the known interactions between several GPCR ligand-containing neuron types and leptin-targeting neurons in the hypothalamus. Finally, we present a new scheme summarizing neuronal networks with regard to feeding regulation in the hypothalamus. Research in this area will play an important role in clarifying neurologically-based causes for appetite dysfunction and establishing therapies for people suffering from such conditions.