Role of proopiomelanocortin neurons and peptides in the regulation of energy homeostasis.

The purpose of this brief review is to highlight recent studies from our laboratory and collaborators based on the analysis of novel strains of mutant mice that further our understanding of the complex regulatory roles of proopiomelanocortin (POMC) neurons and POMC peptides in energy homeostasis. Mouse models that are considered include a transgenic strain with expression of enhanced green fluorescent protein in POMC neurons, facilitating analyses of the cell intrinsic membrane and synaptic properties, and two gene knockout strains exhibiting either a selective absence of beta-endorphin production or a complete loss of all POMC peptides from the pituitary gland and nervous system. Together these studies demonstrate the wide variety of hormonal, metabolic, and transsynaptic signals that converge on the arcuate hypothalamic nucleus and nucleus tractus solitarius to regulate the activity of POMC neurons. Both melanocortin peptides and the opioid beta-endorphin processed from POMC mediate the homeostatic and behavioral responses linked to POMC neuronal circuits.