Fig. 1
Morphine decreases the strength of inhibitory transmission from PV-INs to pyramidal neurons in PrL via MOR, and increases inhibitory synaptic transmission to PV-INs. a Schematic diagram indicating where AAV-Flex-MOR-shRNA-EGFP and AAV-DIO-hChR2(H134R)-mCherry were injected into PrL of PV-Cre or SST-Cre mice. b Representative confocal images showing the pyramidal neurons (PYR, Lucifer yellow) in PrL after whole-cell recordings upon optogenetic stimulation of PV- or SST-interneurons co-expressing hChR2-mCherry and shRNA-EGFP. Percentage of pyramidal neurons responsive to light-evoked activation of PV-INs (c: n = 30 cells/5 mice in saline/Scramble group, 33 cells/6 mice in morphine/Scramble group, 35 cells/6 mice in morphine/MOR-shRNA group; χ2 test) or SST-INs (d: n = 24 cells/4 mice in saline/Scramble group, 27 cells/4 mice in morphine/Scramble group, n = 23 cells/4 mice in morphine/MOR-shRNA group; χ2 test) 1 h after saline or 10 mg/kg morphine treatment. e–h Representative traces and responsive IPSC amplitudes onto pyramidal neurons from PV-INs (e, f: n = 27 cells/5 mice in saline/Scramble group, 29 cells/6 mice in morphine/Scramble group, 30 cells/6 mice in morphine/MOR-shRNA group; One-way ANOVA by the Bonferroni’s post-hoc test, F(2,83) = 5.508, P = 0.0057) or SST-INs (g, h: n = 23 cells/4 mice in saline/Scramble group, 23 cells/4 mice in morphine/Scramble group, 22 cells/4 mice in morphine/MOR-shRNA group; One-way ANOVA by the Bonferroni’s post-hoc test, F(2,65) = 1.505, P = 0.2297) 1 h after saline or morphine (10 mg/kg, i.p.) treatment in PrL slices expressing Scramble or MOR-shRNA. EYFP+ cells in PrL were recorded in acute slice from SST-Cre::EYFP or PV-Cre::EYFP mice 12 h after saline or morphine (10 mg/kg, i.p.) injection. Representative traces (i, j), cumulative probability distribution and average amplitude (k, l), and frequency (m, n) of mIPSCs recorded from SST-INs (n = 22–27 cells/4 mice in each group) and PV-INs (n = 36–40 cells/7–8 mice in each group; Mann–Whitney U test for the average and two-sample Kolmogorov–Smirnov test for cumulative probability). Representative AP traces and number of induced spikes in SST-INs (o, p) or PV-INs (q, r) (o, p: n = 35 cells/7 mice; current: F(25,1700) = 191, P < 0.0001, treatment: F(1,68) = 15.84, P = 0.0002, interaction: F(25,1700) = 9.079, P < 0.0001; q, r: n = 29–30 cells/6 mice; current: F(25,1425) = 192.9, P < 0.0001, treatment: F(1,57) = 7.959, P = 0.0066, interaction: F(25,1425) = 2.822, P < 0.0001; two-way RM ANOVA by the Bonferroni’s post-hoc test) in PrL after saline or morphine injection. Data are presented as mean ± S.E.M; *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001
