Lowering glucose level elevates Ca2+i in hypothalamic arcuate nucleus NPY neurons through P/Q-type Ca channel activation and GSK3β inhibition

摘要

To identify the mechanisms underlying the elevation of intracellular Ca2+ level ([Ca2+]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.[Ca2+]i was measured using fura-2 AM.Ca2+ 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 [Ca2+]i in ARC neurons,but not in hippocampal and cortical neurons.The low-glucose induced elevation of [Ca2+]i in ARC neurons depended on extracellular Ca2+,and was blocked by P/Q-type Ca2+channel blocker ω-agatoxin TK (100 nmol/L),but not by L-type Ca2+ channel blocker nifedipine (10μmol/L) or N-type Ca2+ channel blocker ω-conotoxin GVIA (300 nmol/L).Lowering glucose level increased the peak amplitude of high voltage-activated Ca2+ current in ARC neurons.The low-glucose induced elevation of [Ca2+]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).Conclusion:Lowering glucose level enhances the activity of P/Q type Ca2+ channels and elevates [Ca2+]i level in hypothalamic arcuate nucleus neurons via inhibition of GSK3β.