Amplitude distribution of spontaneous cholinergic and serotonergic synaptic currents. Spontaneous EPSCs were completely abolished in the presence of TTX (3 μm); distributions thus do not represent miniature synaptic currents but most likely action potential-evoked events. A, Spontaneous serotonergic currents recorded from a P8 interneuron. B, Serotonergic events recorded from a P27 layer 3 pyramidal cell.C, D, Spontaneous nicotinic EPSCs recorded from a P30 layer 5 pyramidal cell (C) and a P15 layer 2/3 pyramidal cell (D). All events were recorded in the presence of glutamate and GABA receptor antagonists and DHβE (100 μm) or ICS (10 nm).