title: Separate systems for serotonin and leptin in appetite control.
abstract: Appetite control involves an integration of the drive signals arising form energy stores in the body with the satiety signals generated by periodic episodes of food consumption. Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the processes of within-meal satiation and postmeal satiety (5-HT1B and 5-HT2C postsynaptic receptors) which are concerned with the signals arising form the pattern of food intake. Central nervous system (CNS) 5-HT is sensitive to circulating levels of the precursor tryptophan, certain macronutrients and peripheral satiety factors such as cholecystokinin (CCK) and enterostatin. Hypothalamic 5-HT receptor systems inhibit neuropeptide Y (NPY), a potent stimulator of hunger and food intake. In contrast to the linking of 5-HT with the consequences of food ingestion, the hormone leptin (OB protein) is regarded as a signal linking adipose tissue status with a number of key CNS circuits. Leptin itself stimulates CNS leptin receptors (OB-r receptor) which link with pro-opiomelanocortin (POMC)/ MC-4 receptors. The effects of leptin may also be modulated by factors such as the corticotrophin-releasing factor (CRF), cocaine and amphetamine-regulated transcript (CART), orexins and galanin. Very little evidence exists to support any direct link between the actions of 5-HT and leptin, suggesting that they are separate systems. 5-HT is a part of an integrated network for short-acting satiety signals (episodic in nature), and leptin is a hormonal indicator of long-term (tonic) energy reserves. At a conceptual level, these may represent the distinction between 'satiety' and 'drive'. Interestingly, both 5-HT and leptin modulate the action of NPY, which may form a part of a common output pathway for the expression of appetite.
authors.affiliation: Department of Psychology, University of Liverpool, UK. j.c.g.halford@liverpool.ac.uk
authors.forename: J C
authors.initials: JC
authors.lastname: Halford
authors.forename: J E
authors.initials: JE
authors.lastname: Blundell
mesh_terms: D000818:Animals; D001066:Appetite / Q000502:physiology*; D002490:Central Nervous System / Q000502:physiology; D004435:Eating / Q000502:physiology; D006801:Humans; D020738:Leptin / Q000502:physiology*; D009478:Neuropeptide Y / Q000502:physiology; D019518:Postprandial Period / Q000502:physiology; D012527:Satiation / Q000502:physiology*; D012528:Satiety Response / Q000502:physiology; D012701:Serotonin / Q000502:physiology*
chemical_list: D020738:Leptin; D009478:Neuropeptide Y; D012701:Serotonin