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. 2015 May 8;9:74. doi: 10.3389/fnsys.2015.00074

Figure 4.

Figure 4

Innervation by major SCN afferents. A simplified diagram showing the development of major SCN afferents from the intrinsically photosensitive retinal ganglion cells (ipRGCs) of the retina, raphe nuclei, and intergeniculate leaflet (IGL). (A) ipRGCs first begin to innervate the vlSCN ipsilaterally at birth (mouse/rat P0-P1) or shortly thereafter (hamster P3). The raphe nuclei first innervate the SCN simultaneously (mouse P0, hamster P3). (B) A few days later, ipRGC innervation of the SCN becomes noticeably denser and broader, with the first contralateral projections appearing in the ventromedial SCN (mouse/rat P4), as raphe innervation also builds. (C) By roughly a week into postnatal SCN development, raphe innervation has become fairly dense (mouse P5, hamster P6), ipRGC contralateral and ipsilateral ipRGC innervation domains are commingled (mouse P7), and the earliest Npy signal from the IGL is detectable (hamster P7, rat P10). Many of the IGL and raphe projections converge, a trend that persists through adulthood. (D) In the following few weeks, more-or-less adult SCN innervation by the raphe (mouse P10), ipRGC (mouse P14), and IGL (rat P20) projections become apparent.