(A) 100 µM cyclothiazide (CTZ) bath application increases standing inward current of this OFF UBC and is blocked by 5 µM NBQX. Note increase in noise in CTZ, presumably due to increased AMPAR activity. (B) CTZ increased inward current in OFF UBCs, indicating ambient level of AMPAR desensitization. Wilcoxon signed rank: control vs CTZ, p=0.014, n = 16; paired t-test: CTZ vs CTZ+NBQX, p=0.025, n = 11. (C) CTZ increased inward current in ON UBCs. Paired t-tests: control vs CTZ, p=0.0001, n = 16; CTZ vs CTZ+NBQX, p=0.001, n = 12. (D) There was no significant effect of CTZ on the holding current of granule cells: Friedman test: p=0.264, n = 12. (E) The effect of CTZ on OFF and ON UBCs was not different, but both were significantly different than on GrCs. Mann–Whitney test: OFF UBCs vs GrCs, p<0.0001, n = 29; unpaired t-tests: ON UBCs vs GrCs, p=0.001, n = 29. OFF UBCs vs ON UBCs, p=0.809, n = 32. (F) ON UBC synaptic responses to 50 Hz, 10× electrical stimulation and response after CTZ. Right: EPSCs evoked during 50 Hz stimulation, magnified. The first EPSC became much larger, indicating that ambient glutamate desensitizes AMPARs. (G) CTZ increased the EPSC amplitude 2.3 ± 0.8 fold (mean ± SD), paired t-test, p=0.006, n = 8. The charge during the 50 Hz, 10× stimulation, and the long inward tail increased 9.3 ± 7.0 fold (mean ± SD). Paired t-test, p<0.0001, n = 8.