Fig. 4: In vivo synaptic transmission of PV and SST cells onto M1 pyramidal cells.

a In vivo experimental setup. b Juxtacellular recordings of opto-identified PV and SST interneurons in sham and 6-OHDA-lesioned Sst::ChR2 and PV::ChR2 anesthetized mice. Representative raster plots and spontaneous activity of SST and PV interneurons (boxplots and individual neurons) show similar activity in sham and 6-OHDA-lesioned mice (PV: p = 0.8391, n = 32 cells in sham vs n = 14 in 6-OHDA-lesioned mice; SST: p = 0.2112, n = 32 cells in sham vs n = 15 in 6-OHDA-lesioned mice, Wilcoxon unpaired test). Box plots, center: median; box: 25% and 75% quartiles, whiskers: last data point within 1.5* the interquartile range outside of the box. c–i In vivo patch-clamp recordings of M1 pyramidal cells in Sst::ChR2 and PV::ChR2 anesthetized mice. c Representative traces (left) and averaged peak amplitude (top right) of evoked-PSP following single pulse (3 ms) opto-PV or opto-SST. Opto-PV/SST evoked-PSP of similar amplitudes (p = 0.3397, n = 8 vs n = 9, p = 0.8632, n = 7 vs n = 7 and p = 0.8838, n = 8 vs n = 7, for −100, 0 and +100 pA current injection, respectively, unpaired t-test). (bottom right) Opto-PSPs voltage-dependency, which reversed at −71.5 for opto-PV (n = 6) and −75.2 mV for opto-SST (n = 4) (p = 0.0542, unpaired t-test). Calculated chloride reversal: −71.9 mV. d Area, peak amplitude, slope and delay of evoked-PSP by opto-PV (n = 7) or opto-SST (n = 9). In all cases the pulse duration factor had a significant influence (area: F_3,33 = 4.946, p = 0.0060; peak: F_3,33 = 6.206, p = 0.0029; slope: F_3,33 = 2.956, p = 0.0466; delay: F_3,33 = 6.349, p = 0.0016, 2-way repeated measures ANOVA), with no difference between PSP evoked by opto-PV/SST, except for the delay to peak (F_1,11 = 66.39, p < 0.0001). e Representative voltage traces and heatmap of individual cortical neurons normalized activity, and averaged time course for opto-PV (n = 5) or opto-SST (n = 8) at 67 Hz (3 ms pulses); Injected current: +100 pA. Opto-PV/SST both inhibit pyramidal cell activity (p = 0.0392, p = 0.0010 paired t-test), with a lower effect of opto-SST (last 2.5 s, p = 0.0326, Mann–Whitney U test). Peak amplitude (p = 0.2270) (f), delay to trough (p = 0.0124) (g), amplitude (last 100 ms) (p = 0.0384) (h) and Vm variance (p = 0.0371) (i) of the evoked-hyperpolarization by opto-PV/SST at 67 Hz (n = 5 and 8 cells from 4 PV::Chr2 and 6 Sst::ChR2 mice, respectively). All data are presented as mean ± SD. *p < 0.05; ***p < 0.001. All statistical tests are two-tailed.