S100B Secretion in Acute Brain Slices: Modulation by Extracellular Levels of Ca2+ and K+

Hippocampal slices have been widely used to investigate electrophysiological and metabolic neuronal parameters, as well as parameters of astroglial activity including protein phosphorylation and glutamate uptake. S100B is an astroglial-derived protein, which extracellularly plays a neurotrophic activity during development and excitotoxic insult. Herein, we characterized S100B secretion in acute hippocampal slices exposed to different concentrations of K+ and Ca2+ in the extracellular medium. Absence of Ca2+ and/or low K+ (0.2 mM KCl) caused an increase in S100B secretion, possibly by mobilization of internal stores of Ca2+. In contrast, high K+ (30 mM KCl) or calcium channel blockers caused a decrease in S100B secretion. This study suggests that exposure of acute hippocampal slices to low- and high-K+ could be used as an assay to evaluate astrocyte activity by S100B secretion: positively regulated by low K+ (possibly involving mobilization of internal stores of Ca2+) and negatively regulated by high-K+ (likely secondary to influx of K+).