HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Zhu, Y. Articles by Van Gelder, R. N. Search for Related Content PubMed PubMed Citation Articles by Zhu, Y. Articles by Van Gelder, R. N.

Melanopsin-Dependent Persistence and Photopotentiation of Murine Pupillary Light Responses

¹From the Department of Ophthalmology and Visual Sciences and ³Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, Missouri.

PURPOSE. To determine the relative contributions of inner and outer retinal photoreception to the pupillary light response.

METHODS. Wild-type, retinal degenerate (rd/rd), and melanopsin mutant (opn4^–/–) mice were tested for pupillary light responsiveness by video pupillometry before, during, and after exposure to supersaturating light intensities. Similar lighting protocols were used to probe responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) recorded with multielectrode arrays ex vivo.

RESULTS. Both outer retinal photoreceptors (rods and cones) and inner retinal photoreceptors (intrinsically photosensitive retinal ganglion cells [ipRGCs]) are sufficient to drive the pupillary light response in mice. After supersaturating light exposure, rather than bleaching or adapting, rd/rd mice showed paradoxical potentiation of responses to subsaturating light exposure. opn4^–/– mice, in contrast, could not sustain pupillary constriction under continuous bright illumination, and showed desensitization after bright-light exposure. Both the intensity of light necessary to induce potentiation and the spectral sensitivity for sustained and potentiated responses differed from that necessary to trigger pupillary constriction, suggesting that photopotentiation is dependent on a pigment-state distinct from that triggering the pupillary light response itself. Multielectrode array recordings of ipRGCs from rd/rd retinas demonstrated persistent cell firing under continuous light exposure but did not show potentiation.

CONCLUSIONS. Unique photoreceptive properties of intrinsically photosensitive RGCs confer resistance to bleaching and/or adaptation under continuous bright illumination to the pupillary light response and suggest the presence of a photopigment with multiple absorption states.

This article has been cited by other articles:

				B. Lin, A. Koizumi, N. Tanaka, S. Panda, and R. H. Masland Restoration of visual function in retinal degeneration mice by ectopic expression of melanopsin PNAS, October 14, 2008; 105(41): 16009 - 16014. [Abstract] [Full Text] [PDF]

				K. Mawad and R. N. Van Gelder Absence of Long-Wavelength Photic Potentiation of Murine Intrinsically Photosensitive Retinal Ganglion Cell Firing In Vitro J Biol Rhythms, October 1, 2008; 23(5): 387 - 391. [Abstract] [PDF]

				H. M. Cooper and L. S. Mure Expected and Unexpected Properties of Melanopsin Signaling J Biol Rhythms, October 1, 2008; 23(5): 392 - 393. [PDF]

				R. N. Van Gelder and K. Mawad Illuminating the Mysteries of Melanopsin and Circadian Photoreception J Biol Rhythms, October 1, 2008; 23(5): 394 - 395. [PDF]