GABA_AR-mediated inhibition suppresses LTP. A, LTP in perforated patch recordings from mature GCs (n = 6; left) and 4w abGCs (n = 5; right) in GBZ (open symbols), with comparison to results in ACSF (from Fig. 2A, solid symbols). Insets show EPSPs before and after TBS in GBZ. B, Left, Summary data from 25 to 30 min post-TBS. Two-way ANOVA main effect of cell age p < 0.0001; main effect of GBZ p < 0.0001; interaction effect F_(1,24) = 10, p = 0.005; Tukey's post hoc 4w ACSF versus GBZ p < 0.0001, 4w ACSF versus M ACSF p = 0.001, 4w GBZ versus M GBZ p < 0.0001, M ACSF versus GBZ p = 0.0004. Right, The ratio of LTP in GBZ versus ACSF; unpaired Welch's t test; t_(5.3) = 0.78, p = 0.5) C, Example depolarizations in 6w or M GCs during TBS using whole-cell recordings (n = 6 each). GBZ increases the area (p = 0.0007) regardless of cell age (p = 0.7). There was no significant interaction effect between cell age and GBZ (two-way RM ANOVA; F_(1,10) = 1.2, p = 0.3; Bonferroni's multiple comparisons 6w p = 0.004, M p = 0.048). GBZ also increases the peak amplitude of depolarization. Two-way RM ANOVA, F_(1,10) = 1.7, p = 0.2; main effect of cell age p = 0.8; main effect of GBZ p = 0.0003; Bonferroni's multiple comparisons 6w p = 0.002, M p = 0.04. D, IPSCs in mature GCs evoked by alternating optogenetic stimulation of nNos-ChR2 (top, 1 ms) and electrical stimulation in the ML (bottom) were reduced by DAMGO (gray). Paired t test; t₍₇₎ = 2.61, p = 0.03 (n = 8). E, IPSCs evoked by alternating optogenetic stimulation of PV-ChR2 and electrical stimulation in the GCL (bottom), were suppressed by DAMGO. Paired t test; t₍₇₎ = 3.39, p = 0.01 (n = 8). F, DAMGO enhanced LTP in perforated patch recordings from 4w abGCs (312 ± 22%; n = 5; perforated patch recordings) compared with ACSF (from Fig. 2A; Welch's t test; t_(4.5) = 7.0 p = 0.001).