Fig. 6. Using fiber photometry to measure endogenous CRF release in vivo.

(A) (Left) Schematic diagrams depicting the strategy for virus injection, fiber and cannula implantation, and measurement of CFR1.0 or CRFmut in the PVN. (Right) image showing the expression of CRF1.0 (green) in the PVN and the approximate location of the optic fiber above the PVN; the nuclei were counterstained with 4′,6-diamidino-2-phenylindole (DAPI) (blue). Scale bar, 200 μm. (B to D) Traces (left panels) and summary of the response (right panels) measured in mice expressing CRF1.0 [(B) and (D)] or CRFmut (C); the indicated concentrations of CRF and α-helical CRF 9–41 (AHCRF) were infused through the cannula. (E) Schematic diagram depicting the strategy for virus injection and fiber photometry recording. (F) Image showing the expression of CRF1.0 (green) and the approximate location of the imaging fiber; the nuclei were counterstained with DAPI (blue). Scale bars, 300 μm (left) and 40 μm (right). (G to J) Illustration (G), representative traces (H), average traces per stimulus-response (I), and summary data (J) of the change in CRF1.0 and CRFmut fluorescence measured before and during a 30-s tail lift (G1 to J1) and before and after an intraperitoneal injection of LiCl or saline (G2 to J2); n = 3 to 6 animals.