Microglia are required for iLTP-induced GABA _A Rs plasticity. (a) Left: Iba1⁺ cells are depleted in organotypic slices by PLX3397 (PLX) or Mac1-Saporin (SAP) treatment. Scale bars, 100 μm. Right: Density of Iba1⁺ cells normalized to untreated slices (CTL). n = 4 to 1 independent experiments. Data are mean ± SEM. Each datapoint represents one independent experiment. (b) Confocal images of inhibitory synaptic markers gephyrin, VGAT and GABA_ARα1 in organotypic slices cortical L1. Scale bar, 5 μm. (c) Left: Cumulative fraction of the intensity of GABA_ARα1 clusters at gephyrin⁺ cluster. ****P < 0,0001, Kolmogorov–Smirnoff. Middle: Mean intensity of extrasynaptic GABA_ARα1. Right: Fraction of gephyrin⁺ clusters colocalized to GABA_ARα1. No statistical significance by nested one-way ANOVA followed by Sidak’s multiple comparison test. Results are presented as minimum to maximum box plots. n = 44 to 50 FOVs from six independent experiments. (d) Left: Mean intensity of GABA_ARγ2 clusters at VGAT⁺ clusters around NeuN⁺ cell bodies showing no changes in GABA_ARγ2 at putative somatic L5 synapses upon iLTP. Right: Fraction of VGAT⁺ clusters colocalized to GABA_ARγ2 cluster in putative L5. No statistical significance by nested two-tailed t test. n = 43 to 45 FOVs from six independent experiments. (e) Mean intensity of GABA_ARα1 clusters at gephyrin⁺ cluster showing no suppression of iLTP effect by CX3CL1 neutralizing antibody (n-CX3). n = 63 to 69 FOVs from six independent experiments. *P < 0.05 and **P < 0.01, nested one-way ANOVA followed by Sidak’s multiple comparison test. (d and e) Results are presented as minimum to maximum box-plots.