Relative changes in volume were registered in single cells by using a
microspectrofluorometric equipment and the fluorescent probe fura-2/AM
, excited at its isosbestic point. At this wavelength the probe is ion
-insensitive and the fluorescent signals emitted is dependent on varia
tions in the concentration of the dye. Variations in cell volume thus
lead to changes in fluorescence intensity as the probe concentration i
s changed in the lightened delimited zone selected for each cell. When
changing the excitation wavelength Ca2+ transients can be recorded. G
lutamate (Glu) induced swelling of type I astroglial cells in primary
culture and a parallel intracellular Ca2+ increase was obtained. A Glu
induced swelling was obtained even after blockade of the Glu ionotrop
ic receptors with NBQX, suggesting that activation of ionotropic recep
tors might not be necessary for swelling to occur. On the other hand,
blockade of the Glu carrier, or of pertussis toxin sensitive G-protein
s reduced the Glu induced swelling. Blockade of Ba2+ or TEA sensitive
K+ channels completely blocked the Glu induced swelling as did also bl
ockade with furosemide of the Na+/K+/Cl- co-transporter. Glu induced s
welling occurred in parallel with intracellular Ca2+ transients but ex
tracellular Ca2+ did not seem necessary for swelling to occur.