TY - JOUR
T1 - Adaptation to steady light by intrinsically photosensitive retinal ganglion cells
AU - Do, Michael Tri Hoang
AU - Yau, King Wai
PY - 2013/4/30
Y1 - 2013/4/30
N2 - Intrinsically photosensitive retinal ganglion cells (ipRGCs) are recently discovered photoreceptors in the mammalian eye. These photoreceptors mediate primarily nonimage visual functions, such as pupillary light reflex and circadian photoentrainment, which are generally expected to respond to the absolute light intensity. The classical rod and cone photoreceptors, on the other hand, mediate image vision by signaling contrast, accomplished by adaptation to light. Experiments by others have indicated that the ipRGCs do, in fact, light-adapt. We found the same but, in addition, have now quantified this light adaptation for the M1 ipRGC subtype. Interestingly, in incremental-flash-on-background experiments, the ipRGC's receptor current showed a flash sensitivity that adapted in background light according to the Weber-Fechner relation, well known to describe the adaptation behavior of rods and cones. Part of this light adaptation by ipRGCs appeared to be triggered by a Ca2+ influx, in that the flash response elicited in the absence of extracellular Ca2+ showed a normal rising phase but a slower decay phase, resulting in longer time to peak and higher sensitivity. There is, additionally, a prominent Ca2+-independent component of light adaptation not typically seen in rods and cones or in invertebrate rhabdomeric photoreceptors.
AB - Intrinsically photosensitive retinal ganglion cells (ipRGCs) are recently discovered photoreceptors in the mammalian eye. These photoreceptors mediate primarily nonimage visual functions, such as pupillary light reflex and circadian photoentrainment, which are generally expected to respond to the absolute light intensity. The classical rod and cone photoreceptors, on the other hand, mediate image vision by signaling contrast, accomplished by adaptation to light. Experiments by others have indicated that the ipRGCs do, in fact, light-adapt. We found the same but, in addition, have now quantified this light adaptation for the M1 ipRGC subtype. Interestingly, in incremental-flash-on-background experiments, the ipRGC's receptor current showed a flash sensitivity that adapted in background light according to the Weber-Fechner relation, well known to describe the adaptation behavior of rods and cones. Part of this light adaptation by ipRGCs appeared to be triggered by a Ca2+ influx, in that the flash response elicited in the absence of extracellular Ca2+ showed a normal rising phase but a slower decay phase, resulting in longer time to peak and higher sensitivity. There is, additionally, a prominent Ca2+-independent component of light adaptation not typically seen in rods and cones or in invertebrate rhabdomeric photoreceptors.
KW - Gain control
KW - Mammal
KW - Melanopsin
KW - Phototransduction
UR - http://www.scopus.com/inward/record.url?scp=84876932863&partnerID=8YFLogxK
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U2 - 10.1073/pnas.1304039110
DO - 10.1073/pnas.1304039110
M3 - Article
C2 - 23589882
AN - SCOPUS:84876932863
SN - 0027-8424
VL - 110
SP - 7470
EP - 7475
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 18
ER -