Lowering glucose level elevates [Ca 2+[ i in hypothalamic arcuate nucleus NPY neurons through P/Q-type Ca 2+ channel activation and GSK3Β inhibition

Abstract

Aim: 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-agatoxin TK (100 nmol/L), but not by L-type Ca 2+ channel blocker nifedipine (10mol/L) or N-type Ca 2+ channel blocker-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 (20mol/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 (20mol/L).Conclusion: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. © 2012 CPS and SIMM. All rights reserved.