Supplementary Figure 4: Histological characterization of viral expression of ChR2 in the LEC, MEC and their axon projections along the anterior–posterior axis of CA1.
From: A distinct entorhinal cortex to hippocampal CA1 direct circuit for olfactory associative learning
(a1,a2) Serial sections of LEC (coronal) and MEC (horizontal), demonstrating the ChR2(-mCherry) expression in LEC and MEC (outlined by dashed lines), respectively. Scale bar, 1 mm. (b1) Representative histology verification of ChR2-expressing axons from the LEC (top) and MEC (bottom) in the hippocampus from anterior (A) to posterior (P) axis, respectively. Scale bar, 1 mm. Note that the ChR2(-mCherry) expressing LEC axons appear an increasing gradient in the CA1 stratum lacunosum-moleculare (SLM) layer along the A−P axis, while that of MEC axons show the opposite pattern. The sections in the dashed line box show the intermingled ChR2-expressing axons from the LEC and MEC projection neurons. (b2) Higher resolution images showing clearer segregation in the DG MO layer and distal−proximal gradients in the CA1 SLM layer of LEC and MEC axons in the boxed regions in b1, Scale bar, 200 μm.
