Oxo-m blocks presynaptically expressed PF-LTP. (A) Delivery of 120 PF stimuli at 8 Hz induced PF-LTP (n = 12). Each data point represents an average of four successive test responses delivered at 0.067 Hz. The arrow indicates the time point at which the tetanization protocol was administered. At the top of this and the other panels in this figure are representative PF-EPSCs produced by averaging 20 traces from the indicated time periods. (Scale bars: 50 ms, 100 pA.) (B) PPF ratio (EPSC2/EPSC1) of the data shown in A (n = 12). (C) Application of oxo-m (7 µM) for 5 min (period of bath application indicated by black bar) caused transient depression of evoked PF-EPSCs (n = 10). (Scale bars: 50 ms, 100 pA.) (D) Application of CCh (5 µM) also depressed PF-EPSCs (n = 4). (Scale bars: 50 ms, 200 pA.) (E) Synapse-specific PF-LTP was induced by applying the tetanization protocol to one PF input while a control pathway was left unstimulated during the induction period (n = 7). (Scale bars: 20 ms, 100 pA.) (F) Application of oxo-m during the induction period blocked potentiation in the tetanized pathway (n = 7). (Scale bars: 20 ms, 100 pA.) Error bars indicate SEM.