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

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.

Morphological plasticity of astroglia: Understanding synaptic microenvironment

“…The GFAP‐positive main branches of an astrocyte make up only ∼15% of its total volume (Bushong et al, 2002), thus leaving the bulk of astroglial morphology largely beyond the diffraction limit of conventional optical microscopy. Structural changes in astroglial filopodia‐like protrusions can be routinely observed using time‐lapse light microscopy in cultured hippocampal or cortical astrocytes (Cornell‐Bell et al, 1990a; Lavialle et al, 2011; Molotkov et al, 2013). In acute brain slices some mobile astrocytic processes can be detected (Hirrlinger et al, 2004; Nishida and Okabe, 2007; Nixdorf‐Bergweiler et al, 1994).…”

Injury and nucleotides induce phosphorylation of epidermal growth factor receptor: MMP and HB-EGF dependent pathway

“…Briefly, cells were incubated in an HEPES-buffered saline solution containing 137 mM NaCl, 5 mM KCl, 4 mM MgCl 2 , 3 mM CaCl 2 ·2H 2 O, 25 mM glucose and 10 mM HEPES (Cornell-Bell et al, 1990) and loaded with the Ca 2+ indicator dye fluo-3/AM (5 μM). The cells were imaged using a Zeiss LSM 510 Axiovert confocal laser scanning microscope equipped with an Argon and 2 HeNe lasers.…”

“…Cells were stimulated with agonist prepared in HEPES-buffered saline and washed with HEPES-buffered saline. Ca 2+ dynamics were evaluated as described (Klepeis et al, 2001;Cornell-Bell et al, 1990).…”

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

“…Astrocytes are capable of widespread intercellular signaling in the form of waves of increased [Ca 2ϩ ] i that are propagated from a single cell to multiple surrounding cells (Ca 2ϩ waves) (Cornell-Bell et al, 1990;Charles et al, 1991). Astrocyte Ca 2ϩ waves may occur spontaneously or may be evoked by a variety of stimuli including mechanical stimulation, electrical stimulation, or neurotransmitters (Charles, 1998).…”