NE selectively modulates excitatory, but not inhibitory, synaptic transmission in a reciprocal P-FS connection. A, The morphological characteristics of a reciprocal pair as well as another unconnected pyramidal neuron were recovered with biocytin labeling. The firing patterns of the pyramidal cell and FS interneuron are displayed in the inset. In this reciprocal P-FS connection, we first recorded the EPSCs in the P-FS connection with the membrane potential of FS held at −70 mV. NE was bath-applied after 5-min baseline recording. Ten minutes after washing the NE, the membrane potential of pyramidal neuron was held at −50 mV and the IPSCs in the FS-P connection were recorded during re-application of NE. B and C, NE bath-application dramatically reduced the EPSC amplitudes in the P-FS connection. D and E, In contrast, NE had no clear effects on the IPSCs in the FS-P synapses.