Fig. 6. Activation of PrL pyramidal cells via excitatory Gq-DREADDs improves the working memory performance of ELA mice.
A–C The expression of AAV2-hM3D(Gq)-mCherry (brown) in the PrL. A A representative image to show that mCherry-expression was specifically located in the PrL. The image was taken from a control mouse. AAV2-hM3D(Gq)-mCherry DREADDs were delivered into the PrL of Thy1-Cre transgenic mice via a glass pipette at 6° oblique (ML = 0 mm). IL: infralimbic; fmi: forceps minor of the corpus callosum; ac: anterior commissure. B, C Verification of CNO activation of Thy1-Cre expressing pyramidal cells in the PrL of ELA mice that were infected with AAV2-hM3D(Gq). AAV2-infected cells (brown) co-expressed (arrowheads) Fos (black) in response to CNO administration. D, E Representative images to show CNO-induced activation of cells in the PrL. Increased Fos-expression was apparent in ELA mice treated with CNO versus vehicle (data shown in the Results). The CNO-induced Fos-expression was limited to the PrL. Brain tissues were harvested 90 min after CNO administration. F–H DREADD-based activation of PrL pyramidal cells improves working memory of ELA mice. Thy1-Cre mice in control and ELA groups received an injection of AAV2-hM3D(Gq) into bilateral PrL. CNO or saline (Veh) was administered 1 h before the behavioral training and testing sessions. CNO had no influence on the spontaneous alternation in control mice but increased the percentage of alternation in ELA mice (F1,15 = 29.33; post hoc test, P = 0.51 in controls and **P < 0.01 in ELA mice) (F). The ELA mice with CNO administration displayed a decreased choice latency at T6 compared to vehicle controls (F1,15 = 21.17; post hoc test, **P < 0.01) (G). No difference in the total times to complete the T1-T6 trials was observed among the four groups (F1,15 = 0.799; post hoc test, P > 0.05) (H). I Administration of CNO did not improve working memory in ELA mice that were infected with a control virus AAV2-DIO-mCherry (Alternation: t7 = 1.21, P = 0.26; Latency: t7 = 0.74, P = 0.48). J, K CNO did not alter locomotion measured in an open-field test (main effect of CNO: F1,14 = 0.02, P = 0.90; main effect of ELA: F1,14 = 0.07, P = 0.79; post hoc test, all P > 0.05) or induce an anxiety-like phenotype in a forced swim test (CNO effect: F1,14 = 0.10, P = 0.75; ELA effect: F1,14 = 0.28, P = 0.60; post hoc test, all P > 0.05) in both control and ELA mice treated with Gq-DREADDs. Scale bars = 700 µm (A), 40 µm (B, C), 200 µm (left panels in D, E), and 30 µm (right panels in D, E).