Figure 4.

mGluR/IICR Contribute to the Positive Control of GABA_AR Clustering through Separate Non-overlapping Mechanisms with Ca²⁺ Influx

(A–C) Inhibition of IICR prevents re-clustering of GABA_AR at synapses after NMDA washout. (A) Examples show GABA_AR γ2 immunoreactivities after 3-min exposure to NMDA (top) or after 15 min of NMDA washout in the presence of DMSO (middle) or 2APB (bottom). Scale bar, 10 μm. (B and C) Quantification of the fluorescence intensity of GABA_ARγ2 before (NMDA) and after washout (Recovery), in the presence or absence of 2APB (B) or MCPG (C), is shown. Values (mean ± SEM) were normalized to their respective control values (n = 30 cells/condition; ^∗∗∗p < 0.005, t-test).

(D–I) Pre-activation of IICR prevents NMDA-mediated dispersion of GABA_AR. Neurons pre-incubated to NMDA (D–F) or DHPG (G–I) were then exposed to NMDA in the presence of DHPG. Images (E and H) and quantifications of synaptic cluster fluorescence intensities (F and I) reveal that DHPG restored GABA_AR clustering only when neurons were pre-treated with DHPG. Scale bars, 10 μm. Values (mean ± SEM) were normalized to their respective control values (n = 30–60 cells per condition; ^∗∗∗p < 0.005, Tukey’s range test in ANOVA).