Different characteristics of cell volume and intracellular calcium ion concentration dynamics between the hippocampal CA1 and lateral cerebral cortex of male mouse brain slices during exposure to hypotonic stress.

The mechanism of brain edema is complex and still remains unclear. Our aim was to investigate the regional differences of cell volume and intracellular Ca2+ concentration ([Ca2+ ]i ) dynamics during hypotonic stress in male mouse hemi-brain slices. Brain slices were loaded with the fluorescence Ca2+ indicator fura-2, and cell volume and [Ca2+ ]i in the lateral cerebral cortex (LCC) and hippocampal CA1 (CA1) region were measured simultaneously during exposure to hypotonic stress using Ca2+ insensitive (F360) and Ca2+ sensitive fluorescence (F380), respectively. Brain cell swelling induced by hypotonic stress was followed by a regulatory volume change that coincided with an increase in [Ca2+ ]i . The degrees of change in cell volume and [Ca2+ ]i were significantly different between the LCC and CA1. The increase in cell volume and [Ca2+ ]i in the LCC, but not in the CA1, was decreased by the transient receptor potential channel blockers LaCl3 and GdCl3 . The increase in [Ca2+ ]i in both the LCC and CA1, was significantly decreased by the intracellular Ca2+ modulators thapsigargin and xestospongin C. The K+ channel activator isoflurane and Cl- channel blocker NPPB significantly decreased [Ca2+ ]i in the LCC. This study demonstrated that, between cells located in the LCC and in the CA1, the characteristics of brain edema induced by hypotonic stress are different. This can be ascribed to the different contribution of volume sensitive G-protein coupled receptor and stretch sensitive Ca2+ channels.