Glutamate Induces Calcium Waves in Cultured Astrocytes: Long-Range Glial Signaling

TLDR

The discovery that astrocytes possess glutamate‑sensitive ion channels suggested a previously unrecognized signaling role for these cells. Two glutamate receptor subtypes—one favoring quisqualate and releasing calcium from intracellular stores, the other favoring kainate and promoting membrane calcium influx—are implicated in this response. Cultured hippocampal astrocytes exhibit rapid, oscillatory calcium elevations upon glutamate stimulation that propagate as waves within and between cells, implying that astrocyte networks may constitute a long‑range signaling system.

Abstract

The finding that astrocytes possess glutamate-sensitive ion channels hinted at a previously unrecognized signaling role for these cells. Now it is reported that cultured hippocampal astrocytes can respond to glutamate with a prompt and oscillatory elevation of cytoplasmic free calcium, visible through use of the fluorescent calcium indicator fluo-3. Two types of glutamate receptor—one preferring quisqualate and releasing calcium from intracellular stores and the other preferring kainate and promoting surface-membrane calcium influx—appear to be involved. Moreover, glutamate-induced increases in cytoplasmic free calcium frequently propagate as waves within the cytoplasm of individual astrocytes and between adjacent astrocytes in confluent cultures. These propagating waves of calcium suggest that networks of astrocytes may constitute a long-range signaling system within the brain.