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. Author manuscript; available in PMC: 2023 Jan 8.
Published in final edited form as: Front Neuroendocrinol. 2019 Apr 16;54:100746. doi: 10.1016/j.yfrne.2019.04.003

Fig. 3.

Fig. 3.

Neural circuitry of the circadian system. Photic information enters the retina and stimulates melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). Photic information is directly relayed to the suprachiasmatic nucleus (SCN) and intergeniculate leaflet (IGL) via the retinohypothalamic tract (RHT), a glutamatergic and/or pituitary adenylate cyclase-activating peptide (PACAP) pathway. The SCN also receives non-photic information from an NPY-ergic pathway from the as well as from a 5-HTergic pathway from the dorsal raphe and median raphe nuclei (DRN and MRN, respectively).