Figure 2.
Functional Characterization of Granule Cell (GC) Firing Properties in Dock10-Cre;Ai32 Slices
(A–E) ChR2-EYFP expression (green) in the dentate gyrus (DG) and in mossy fibers to the CA3. Cell nuclei visualized by DAPI (cyan; A and B). ChR2-EYFP (green) in synaptoporin-positive MFBs (magenta) in the CA3 (C–E).
(F–H) Percentage of Cre-recombinase positive (G, white) DAPI-stained nuclei (F, cyan) and (G, cyan outlines) in the DG. Scatterplot (H, top) and cumulative distribution (H, bottom) indicating the quantification of Cre-signal in CA3 pyramidal (CA3, “background signal”) and DG granule cells (DG; “real signal”). More than 91% of GCs express (red line) Cre above threshold (H, CA3, n = 3 slices; 40.61 a.u. ± 6.28; CA3, n = 3; 83.67 a.u. ± 4.67).
(I) Experimental setup for measuring light evoked GC action potential (AP) properties (J–Q).
(J) Exemplary recording in which increasing light pulse (LP) duration (1 to 10 ms) triggered zero to two APs (top representation) and a ChR2-mediated current (IChR2) of increasing size and duration (bottom representation).
(K), Summary data on AP firing in response to 2 ms or 5 ms LPs at 2.72 and 10.9 mW/mm2 (n = 10 cells).
(L and M) Latency of APs evoked by a 5 ms LP at 2.72 (5.72 ± 0.32 ms, n = 10) and 10.9 mW/mm2 (2.55 ± 0.08 ms, n = 10), respectively, measured from the onset of the LP.
(N), AP firing reliability during 100 LP trains (20 Hz) for different light intensities (2 ms, n = 10; 5 ms, n = 10).
(O–Q) Exemplary recordings from three different GCs of AP trains in response to 100 × 5 ms LPs at 20 Hz (O), 5.45 mW/mm2 (P), and 9.08 mW/mm2 (Q). The first (bottom left) and last (bottom right) five APs are shown at an expanded timescale.
Scale bars: 500 μm (B); 10 μm (E); 100 μm (G). Error bars indicate mean ± SEM.
See also Figures S3 and S4.