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. 2020 Sep 8;32(10):108123. doi: 10.1016/j.celrep.2020.108123

Figure 1.

Figure 1

Anatomical Connectivity between PPN and MEC

(A–C) Top row: sagittal sections showing schematic of target areas for tracer injections (gray). Red rectangles indicate location of respective panels in lower row.

(A) Injection of retrograde tracer fast blue (FB) in MEC (white dashed line) with fluorescent Nissl counterstaining. The injection spans all cortical layers.

(B) Injection of the anterograde tracer biotinylated dextran amine (BDA) in PPN in the same animal as in (A). Anatomical boundaries of PPN (white dashed line) defined by choline acetyltransferase (ChAT) immunofluorescence staining. Note the absence of FB-labeled neurons in PPN.

(C) Overlap between PPN axonal projections (BDA) and MEC-projecting neurons (FB) in HDB (white dashed line), as defined by ChAT immunofluorescence staining. In addition to the presence of PPN projections outside HDB, note the substantial amount of labeled axons within the anatomical borders of HDB, some of which close to MEC-projecting FB-labeled neurons (see Dii for further evidence of double-labeling proximity).

(D–F) Additional brain areas displaying double BDA and FB staining.

(D) Left: BDA/FB labeling along the dorsoventral axis of the medial septum, vertical and horizontal limbs of the diagonal band region (MS, VDB, HDB, white dashed line, boundary defined by ChAT immunofluorescence staining, different case than A–C). Red squares represent high-magnification regions of interest (ROIs) shown to the right, displaying BDA/FB staining, respectively, in MS (i) and HDB and directly adjacent VDB (ii).

(E and F) Low-magnification (top) and high-magnification ROIs (red squares, bottom) showing BDA/FB labeling in the supramammillary nucleus (SuM) (E) and in the nucleus reuniens (Re) of the thalamus (F) (same case as in A–C).

ac, anterior commissure; AM, anteromedial thalamic nucleus; AMV, anteromedial thalamic nucleus, ventral part; f, fornix; ML, medial mammillary nucleus, lateral part; mp, mammillary peduncle; mt, mammillothalamic tract; PMD, premammillary nucleus, dorsal part; Sub, submedius thalamic nucleus; VRe, ventral reuniens thalamic nucleus; VTM, ventral tuberomammillary nucleus; 3V, third ventricle. Scale bars: 500 μm.