The excitability of PIC neurons and their projections to the BLA and VM are enhanced in SNI mice. A–D, Schematic diagram of representative coronal sections showing virus injection into the VM (AAV-retro-hSyn-mCherry) and BLA (AAV-retro-hSyn-eGFP) to retrogradely label PIC neurons. E, F, Numbers of PIC→VM (red) and PIC→BLA (green) neurons at a series of anterior to posterior levels (n = 5 mice). G–L, Representative images of GFP(+) (G, top panel), mCherry(+) (I, top panel), or GFP(+)–mCherry(+) (K, top panel) PIC neurons for whole-cell current-clamp recording. Representative traces (G, I, and K, bottom panels) and summary (H,J,L) of depolarizing current injection-evoked firing in PIC→BLA neurons, PIC→VM neurons, and colabeled PIC→BLA→VM neurons 4 weeks after sham (black) or SNI (red) surgery. H, F_(1,91) = 134.2, p < 0.0001; J, F_(1,247) = 128.2, p < 0.0001; L, F_(1,104) = 72.96, p < 0.0001. M, Representative images showing the injection of AAV-CaMKII-ChR2-eYFP into the PIC and eYFP-labeled fibers in the VM and BLA. N, O, Example traces (N) and peak amplitude (O) of blue light-evoked (5 ms, 2 mW) photo-EPSCs in BLA neurons from sham and SNI mice 2 weeks after surgery. Amplitude (O), t = 4.82, p < 0.0001. n = 14 cells from four mice in each group. P–R, Representative traces (P) and summary of evoked firing rate (Q) and summary of resting membrane potentials (R) in BLA neurons receiving PIC projections in sham or SNI mice 2 weeks after sham or SNI surgery. Q, F_(1,15) = 20.08, p = 0.0004, n = 5 mice in each group; R, t = 3.59, p = 0.0022. Sham, n = 12. SNI, n = 7. S,T, Example traces (S) and peak amplitude (T) of blue light-evoked (5 ms, 2 mW) photo-EPSCs in VM neurons from sham and SNI mice 2 weeks after surgery. Amplitude (T), t = 2.69, p = 0.016. n = 9 cells in each group. U–W, Representative traces (U) and summary of evoked firing rate (V) and summary of resting membrane potentials (W) in VM neurons receiving PIC projections in sham or SNI mice 2 weeks after surgery. V, F_(1,19) = 13.99, p = 0.0014, n = 5 mice in each group. W, t = 0.28, p = 0.78. Sham, n = 12. SNI, n = 9. *p < 0.05. **p < 0.01. Two-way repeated measures ANOVA for H, J, L,Q, and V. Two-tailed unpaired t test for O, T, R, and W. Scale bar, 100 µm.