Physiologic Diversity and Development of Intrinsically Photosensitive Retinal Ganglion Cells

All intrinsically photosensitive retinal ganglion cells (ipRGCs) in mice rely on melanopsin for photosensitivity.

• Three distinct types of ipRGCs are identified in the postnatal day 8 murine retina: type I, type II, and type III.
• Type I ipRGCs exhibit slow onset, sensitivity, and fast off responses, while type II ipRGCs are slow onset, insensitive, and slow off.
• Type III ipRGCs show rapid onset, sensitivity, and very slow off responses.
• Intrinsic light responses in ipRGCs begin as transient and insensitive at postnatal day zero (P0), with increased sensitivity and persistence observed by postnatal day six (P6).
• These findings indicate that ipRGCs are the first light-sensitive cells in the murine retina and reveal a previously unrecognized diversity within this cell population.

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