Fig. 4.

Glucocorticoid-induced suppression of excitation requires postsynaptic calcium mobilization. A. Running time histogram of the effect on mEPSC frequency of Dex with and without BAPTA in the patch electrode. The Dex-induced decrease in mEPSC frequency was blocked with BAPTA in the electrode. B. Summary bar graph of the effects of calcium blockers on the Dex-induced decrease in mean normalized mEPSC frequency. Dexamethasone had no effect on the mEPSC frequency following intracellular application of BAPTA or extracellular application of a nominally zero calcium solution (0Ca²⁺) but retained its suppressive effect on mEPSC frequency in cells treated with the voltage-gated calcium channel blockers cadmium (Cd²⁺, 200 μM) and nifedipine (Nifed, 10 μM) applied in the perfusion bath. C. Summary bar graph of the effects of blockers of intracellular calcium mobilization. Inhibition of the SERCA intracellular calcium transporter with intracellular thapsigargin application via the patch pipette blocked the Dex-induced suppression of mEPSC's (Thaps, 5 μM). Inhibition of the IP3 receptor antagonist Xestospongin C also blocked the Dex-induced decrease in mEPSC frequency (XestoC). *, p < 0.05 compared to baseline; **, p < 0.01 compared to baseline; #, p < 0.05 vs Dex).