title: Lowering glucose level elevates [Ca2+]i in hypothalamic arcuate nucleus NPY neurons through P/Q-type Ca2+ channel activation and GSK3β inhibition.
abstract: OBJECTIVE
  To identify the mechanisms underlying the elevation of intracellular Ca(2+) level ([Ca(2+)](i)) induced by lowering extracellular glucose in rat hypothalamic arcuate nucleus NPY neurons.
  
  
  METHODS
  Primary cultures of hypothalamic arcuate nucleus (ARC) neurons were prepared from Sprague-Dawley rats. NPY neurons were identified with immunocytochemical method. [Ca(2+)](i) was measured using fura-2 AM. Ca(2+) current was recorded using whole-cell patch clamp recording. AMPK and GSK3β levels were measured using Western blot assay.
  
  
  RESULTS
  Lowering glucose level in the medium (from 10 to 1 mmol/L) induced a transient elevation of [Ca(2+)](i) in ARC neurons, but not in hippocampal and cortical neurons. The low-glucose induced elevation of [Ca(2+)](i) in ARC neurons depended on extracellular Ca(2+), and was blocked by P/Q-type Ca(2+)channel blocker ω-agatoxin TK (100 nmol/L), but not by L-type Ca(2+) channel blocker nifedipine (10 μmol/L) or N-type Ca(2+)channel blocker ω-conotoxin GVIA (300 nmol/L). Lowering glucose level increased the peak amplitude of high voltage-activated Ca(2+) current in ARC neurons. The low-glucose induced elevation of [Ca(2+)](i) in ARC neurons was blocked by the AMPK inhibitor compound C (20 μmol/L), and enhanced by the GSK3β inhibitor LiCl (10 mmol/L). Moreover, lowering glucose level induced the phosphorylation of AMPK and GSK3β, which was inhibited by compound C (20 μmol/L).
  
  
  CONCLUSIONS
  Lowering glucose level enhances the activity of P/Q type Ca(2+)channels and elevates [Ca(2+)](i) level in hypothalamic arcuate nucleus neurons via inhibition of GSK3β.
authors.affiliation: Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.forename: Na
authors.initials: N
authors.lastname: Xie
authors.forename: Chao
authors.initials: C
authors.lastname: Huang
authors.forename: Jun-qi
authors.initials: JQ
authors.lastname: Zhang
authors.forename: Zhuang-li
authors.initials: ZL
authors.lastname: Hu
authors.forename: Lan
authors.initials: L
authors.lastname: Ni
authors.forename: You
authors.initials: Y
authors.lastname: Jin
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Jian-guo
authors.initials: JG
authors.lastname: Chen
authors.forename: Li-hong
authors.initials: LH
authors.lastname: Long
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D015415:Biomarkers / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D007150:Immunohistochemistry; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D009478:Neuropeptide Y / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D055372:AMP-Activated Protein Kinases; D015415:Biomarkers; D002118:Calcium; D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D005947:Glucose; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D009478:Neuropeptide Y; D047428:Protein Kinase Inhibitors; C000605508:Gsk3b protein, rat