title: Orexin excites GABAergic neurons of the arcuate nucleus by activating the sodium--calcium exchanger.
abstract: The neuropeptides orexins/hypocretins are essential for normal wakefulness and energy balance, and disruption of their function causes narcolepsy and obesity. Although much is known of the role of orexins in sleep/wake behavior, it remains unclear how they stimulate feeding and metabolism. One of the main targets of orexinergic neurons is the arcuate nucleus (ARC) of the hypothalamus, which plays a key role in feeding and energy homeostasis. By combining patch-clamp and RT-multiplex PCR analysis of individual neurons in mouse brain slices, we show that an electrophysiologically distinct subset of ARC neurons coexpress orexin receptors and glutamate decarboxylase-67 and are excited by orexin. Acting on postsynaptic orexin type 2 receptors, orexin activates a sodium-calcium exchange current, thereby depolarizing the cell and increasing its firing frequency. Because GABA is a potent stimulus for feeding, in both the ARC and its main projection site, these results suggest a mechanism for how orexin may control appetite.
authors.affiliation: University Laboratory of Physiology, Oxford, OX1 3PT, United Kingdom. denis.burdakov@physiol.ox.ac.uk
authors.forename: Denis
authors.initials: D
authors.lastname: Burdakov
authors.forename: Birgit
authors.initials: B
authors.lastname: Liss
authors.forename: Frances M
authors.initials: FM
authors.lastname: Ashcroft
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D004734:Energy Metabolism / Q000502:physiology; D005968:Glutamate Decarboxylase / Q000096:biosynthesis; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000494:pharmacology*; D064446:Orexin Receptors; D000068797:Orexins; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000096:biosynthesis; D019831:Sodium-Calcium Exchanger / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D002614:Chelating Agents; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D019831:Sodium-Calcium Exchanger; D004533:Egtazic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium