THE ROLE OF PEPTIDES IN APPETITE REGULATION ACROSS SPECIES

The regulation of food intake is a complex process involving both a ce ntral feeding drive and a peripheral satiety system. The endogenous ka ppa opioid dynorphin, is an important central stimulator of feeding. O piates are involved in feeding regulation of a variety of species incl uding amoeba, molluscs, mammals and birds. Opioids appear to regulate a variety of behaviors necessary to allow the animal to successfully o btain food. Some species lack an opioid feeding system. Cholecystokini n (CCK) is the prototypic satiety agent which decreases feeding in mul tiple species from molluscs to humans, CCK also enhances memory and th us may play a role in allowing the animal to remember the details of a successful hunt. Alterations in the photoperiod can alter the respons e to satiety peptides raising the possibility that these peptides may play a role in pre-hibernation anorexia. Other important neurotransmit ters involved in generating the feeding drive are neuropeptide Y and n itric oxide. Studies across species suggest that the central feeding c ommand system is the basic feeding system, which with the organism's d evelopment of the need for satiety periods is held in check by the int roduction of a variety of peripheral satiety systems.