Effects of sGC inhibition and NO deprivation on spontaneous synaptic currents. A, Effects of sGC inhibition (n = 17 cells) and NO deprivation (n = 9 cells) on the amplitude of EPSCs and IPSCs under control and low-Mg²⁺ conditions. Neither block of sGC nor NO deprivation had an effect on EPSC amplitude in normal ACSF compared with untreated slice cultures (n = 17 cells). EPSC and IPSC amplitude increased significantly in control and ODQ-treated under low-Mg²⁺ condition. In contrast, the increase in both EPSC and IPSC amplitudes was abolished in NO-deprived slice cultures. B, Effects of sGC inhibition and NO deprivation on the frequency of EPSCs and IPSCs under control and low-Mg²⁺ conditions. NO deprivation significantly decreased EPSC frequency in normal ACSF as well as IPSC frequency under control and low-Mg²⁺ conditions. In contrast, IPSC and EPSC frequencies were not affected by ODQ treatment (10 and 50 μm). C, Effects of NO deprivation on spontaneous synaptic activity in the same cell under low-Mg²⁺ condition before and after washout of l-NMMA/cPTIO. Both the amplitude and the frequency of the EPSCs and IPSCs were significantly decreased in the presence of l-NMMA/cPTIO. Note that EPSC and IPSC amplitudes in the absence of l-NMMA/cPTIO were on average still smaller than in untreated slice cultures under low-Mg²⁺ condition. IM, Membrane current.