Figure 2.
Knock-out of IP3R2 affects astrocyte but not neuronal GPCR-mediated Ca2+ increases.
A
, Representative Ca2+ traces from astrocytes of Calcium Green AM-loaded hippocampal slices. Regions of interest were placed over the cell bodies of bulk-loaded hippocampal astrocytes to measure Ca2+ increases in response to agonist application (top). Application of ATP (100 μm) or a Gq-linked GPCR agonist cocktail (Ct, 10 μm DHPG, 10 μm histamine, and 10 μm carbachol) elicited Ca2+ responses in astrocytes from littermate control but not IP3R2 KO hippocampal slices. The arrows indicate the astrocyte Ca2+ traces shown in the bottom panels. Thapsigargin (Tg; 2 μm) was used as a control and increased Ca2+ in astrocytes of both littermate control and IP3R2 KOs. Data are presented as fold increases over baseline.
B
, Percentage of astrocytes responding to application of ATP or the Gq-linked GPCR agonist cocktail from all experiments.
C
, Representative Ca2+ traces from CA1 pyramidal neurons patch clamped with internal solution containing Fluo-4 Ca2+ indicator in response to application of a Gq-linked GPCR cocktail (50 μm DHPG, 10 μm histamine, 10 μm carbachol) in the presence of 1 μm TTX to block action potentials.
D
, Amplitude and duration of IP3R-mediated Ca2+ responses in CA1 pyramidal neurons (control, n = 8; IP3R2 KO, n = 6). There were no significant differences for amplitude (left; p = 0.39) or duration (right; p = 0.08). Error bars indicate SEM.