Figure 2
From: Development of melanopsin-based irradiance detecting circuitry
ipRGCs innervate the suprachiasmatic nucleus postnatally. Innervation of the suprachiasmatic nucleus (SCN) begins at P0 and continues throughout the first two postnatal weeks. (A) Labeling of all RGCs in coronal sections with fluorescently labeled cholera toxin B subunit (CTB), one color per eye. Retinal fibers fill the SCN by P7 and innervation becomes bilateral by P14. Note that for CTB labeling, a P0 time point was not possible due to the survival period required for the tracer to label distal axons. (B,C) Labeling of ipRGCs and their axons with both MelanopsinCre/+;Z/AP (B) and MelanopsintauLacZ/+ (C) reveals a similar innervation pattern. (D-F) In contrast, CTB labeling reveals RGC axons have already penetrated the LGN by P1 (D), and genetic labeling of Brn3b-positive RGCs (E) reveals that this subset of RGCs begins entering the pretectum as early as E17 (F). Arrows indicate fibers entering target area. n = 3 or more animals for each time point. OT, optic tract; dashed outlines demarcate the SCN prior to innervation in (A,B). Scale bars: 100 μm (A-C); 500 μm (F).