title: CCK stimulation of GLP-1 neurons involves α1-adrenoceptor-mediated increase in glutamatergic synaptic inputs.
abstract: OBJECTIVE
  Glucagon-like peptide 1 (GLP-1) is involved in the central regulation of food intake. It is produced within the brain by preproglucagon (PPG) neurons, which are located primarily within the brain stem. These neurons project widely throughout the brain, including to the appetite centers in the hypothalamus, and are believed to convey signals related to satiety. Previous work demonstrated that they are directly activated by leptin and electrical activity of the afferent vagus. Another satiety hormone, cholecystokinin (CCK), has also been linked to activation of brain stem neurons, suggesting that it might act partially via centrally projecting neurons from the nucleus tractus solitarius (NTS). The aim of this study was to investigate the neuronal circuitry linking CCK to the population of NTS-PPG neurons.
  
  
  METHODS
  Transgenic mice expressing yellow fluorescent protein (Venus) under the control of the PPG promoter were used to identify PPG neurons in vitro and to record their electrical and pharmacological profile.
  
  
  RESULTS
  PPG neurons in the NTS were excited by CCK and epinephrine, but not by the melanocortin receptor agonist melanotan II. Both CCK and epinephrine acted to increase glutamatergic transmission to the PPG neurons, and this involved activation of α(1)-adrenergic receptors. Inhibition of adrenergic signaling abolished the excitatory action of CCK.
  
  
  CONCLUSIONS
  CCK activates NTS-PPG cells by a circuit involving adrenergic and glutamatergic neurons. NTS-PPG neurons integrate a variety of peripheral signals that indicate both long-term energy balance and short-term nutritional and digestional status to produce an output signal to feeding and autonomic circuits.
authors: Department of Surgery and Cancer, Imperial College London, London, UK.
authors: Kazunari
authors: K
authors: Hisadome
authors: Frank
authors: F
authors: Reimann
authors: Fiona M
authors: FM
authors: Gribble
authors: Stefan
authors: S
authors: Trapp
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002766:Cholecystokinin / Q000031:analogs & derivatives / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D017930:Genes, Reporter; D052216:Glucagon-Like Peptide 1 / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D052336:Proglucagon / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018340:Receptors, Adrenergic, alpha-1 / Q000737:chemistry / Q000378:metabolism*; D011949:Receptors, Cholecystokinin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017470:Receptors, Glutamate / Q000737:chemistry / Q000378:metabolism*; D017552:Solitary Nucleus / Q000166:cytology / Q000378:metabolism
chemical_list: D018377:Neurotransmitter Agents; D020033:Protein Isoforms; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D011949:Receptors, Cholecystokinin; D017470:Receptors, Glutamate; D052336:Proglucagon; D052216:Glucagon-Like Peptide 1; D002766:Cholecystokinin; D004837:Epinephrine