title: Melanopsin-dependent light avoidance in neonatal mice.
abstract: Melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) form a light-sensitive system separate from rods and cones. Direct light stimulation of ipRGCs can regulate many nonimage-forming visual functions such as photoentrainment of circadian rhythms and pupil responses, and can intensify migraine headache in adults. In mice, ipRGCs are light responsive as early as the day of birth. In contrast, their eyelids do not open until 12-13 d after birth (P12-13), and light signaling from rods and cones does not begin until approximately P10. No physiological or behavioral function is established for ipRGCs in neonates before the onset of rod and cone signaling. Here we report that mouse pups as young as P6 will completely turn away from a light. Light-induced responses of ipRGCs could be readily recorded in retinas of pups younger than P9, and we found no evidence for rod- and cone-mediated visual signaling to the RGCs of these younger mice. These results confirm that negative phototaxis is evident before the onset of rod- and cone-mediated visual signaling, and well before the onset of image-forming vision. Negative phototaxis was absent in mice lacking melanopsin. We conclude that light activation of melanopsin ipRGCs is necessary and sufficient for negative phototaxis. These results strongly suggest that light activation of ipRGCs may regulate physiological functions such as sleep/wake cycles in preterm and neonatal infants.
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, CA 94143, USA.
authors.forename: Juliette
authors.initials: J
authors.lastname: Johnson
authors.forename: Vincent
authors.initials: V
authors.lastname: Wu
authors.forename: Michael
authors.initials: M
authors.lastname: Donovan
authors.forename: Sriparna
authors.initials: S
authors.lastname: Majumdar
authors.forename: René C
authors.initials: RC
authors.lastname: Rentería
authors.forename: Travis
authors.initials: T
authors.lastname: Porco
authors.forename: Russell N
authors.initials: RN
authors.lastname: Van Gelder
authors.forename: David R
authors.initials: DR
authors.lastname: Copenhagen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001362:Avoidance Learning / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D006801:Humans; D007231:Infant, Newborn; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D010775:Photic Stimulation; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin