Promotion of GABA transmission onto MCs by NRG1. A, Schematic diagram showing the slice recording paradigm of MCs. B, Representative traces of mitral cell mIPSC recorded before, during, and after NRG1 application. C, D, Summary of mIPSC frequency (C) and amplitude (D) before, during, and after NRG1 application (n = 7 cells from 3 mice). E, Representative traces of mitral cell mEPSC recorded before, during, and after NRG1 application. F, G, Summary of mEPSC frequency (B) and amplitude (C) before, during, and after NRG1 application (n = 7 cells from 3 mice). H, Representative traces of mitral cell eIPSC before, during, and after NRG1 application. I, Summary of mitral cell eIPSC showing the increased amplitude after NRG1 application, which can be washed out (n = 6 cells from 3 mice). J, Representative traces of paired-pulse (interval, 50 ms) stimuli before and during NRG1 application. K, Summarized data showing the decreased mitral cell eIPSC PPR by NRG1 (n = 12 neurons from 4 mice; paired t test). L, Representative traces of GCL-ErbB4⁺ neurons in responding to step current injection in the presence of NRG1. M, Input–output curve showing the excitability of GCL-ErbB4⁺ neurons in the presence of NRG1 (n = 7 cells from 3 mice). N, Representative traces of GL-ErbB4⁺ neurons in responding to step current injection in the presence of NRG1. O, Input–output curve showing the excitability of GL- ErbB4⁺ neurons in the presence of NRG1 (n = 7 cells from 3 mice). *p < 0.05. **p < 0.01.