Glutamate-induced intracellular calcium oscillations in astrocytes with confocal microscopy

Abstract

Changes in the intracellular Ca²⁺ concentration ([Ca²⁺]i) play a crucial role involved in the modulation of signal transduction, development, and plasticity in the CNS. Glial cells can respond to various stimuli with an increase in [Ca²⁺]i. In this paper, we used confocal microscopy to study calcium transient induced by glutamate in cultured astrocytes. Firstly, 100 μM glutamate induced long-time intracellular calcium oscillations in astrocytes and only a single spike under calcium-free solution. When the concentration of glutamate decreased to 1 μM, only a single spike could be induced. It shows that intracellular calcium oscillations depend on agonist concentration and extracellular Ca²⁺. Secondly, we investigated amplitude of responses under different stimulation. The amplitude of initial peak induced by 100 μM glutamate decreased in Ca²⁺-free condition, whereas the duration of kinetics was prolonged. But both the amplitude and area of a single spike induced by 1 μM Glu decreased in Ca²⁺-free condition. The results show that areaof peak is more accurate than amplitude to display transients of [Ca²⁺]i. All results above suggest that astrocytes are not passive, they display diverse temporal and spatial increases in [Ca²⁺]i in response to a variety of stimuli. These [Ca²⁺]i increases provide a possible means for information coding.