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. 2022 Mar 1;15:843754. doi: 10.3389/fnmol.2022.843754

FIGURE 4.

FIGURE 4

ZI PV neurons negatively regulate scratching behaviors during acute itch. (A) Schematic illustration of viral injection for chemogenetic modulation of ZI PV neurons. (B) Histological verification of viral expression in the ZI in a representative mouse with AAV-DIO-hM3Dq-mCherry injection. Scale bar = 250 μm. (C) Representative photographs showing the expression of PV (green) in hM3Dq-positive (red) neurons in the ZI of PV-Cre mice. (D) Representative photographs showing the expression of FOS (green) in hM3Dq-positive (red) neurons in the ZI of PV-Cre mice. (E) Quantification of FOS-expressing neurons in mice with AAV-hM3Dq and AAV-mCherry injection showed CNO injection increased FOS expression in ZI PV neurons in the mice in AAV-hM3Dq group. n = 3 mice per group, three sections per mouse. Unpaired T-test. t = –14.44, P < 0.001. (F,G) Chemogenetic activation of ZI PV neurons reduces scratching behaviors induced by histamine (F) and chloroquine (G), while inhibition of them exerts no effect on scratching behaviors. One-way ANOVA with post hoc LSD test for multiple comparisons. For the analysis of histamine-induced itch, F(2,6) = 10.599, P = 0.001. n = 6 mice in EGFP and hM4Di groups and 7 in hM3Dq group. For the analysis of chloroquine-induced itch, F(2,6) = 13.341, P < 0.001. n = 6 mice in EGFP and hM4Di groups and 7 in hM3Dq group. n = 7 mice in EGFP and hM4Di groups and 8 in hM3Dq group. ∗∗∗P < 0.001, ∗∗P < 0.01.