Electroretinography of wild-type and Cry mutant mice reveals circadian tuning of photopic and mesopic retinal responses.
Attempts to understand circadian organization in the mammalian retina have concentrated increasingly on the mouse. However, rather little is known regarding circadian control of retinal light responses in this species. Here, the authors address this deficit using electroretinogram (ERG) recordings in C57BL/6 mice to evaluate rhythmicity in the wild-type retina and to identify the consequences of circadian clock loss in Cry1(- /-)Cry2(-/-) mice. They observe a circadian rhythm in the ERG waveform under light-adapted, cone-isolating conditions in wild-type mice, with b-wave speed and amplitude and the total power of oscillatory potentials all enhanced during the day. Wild types also exhibited a circadian dependence to ERG amplitude under dark-adapted conditions, but only when the flash stimulus was sufficiently bright to lie within the response range of cones. Cry1(-/ -)Cry2(-/-) mice lacked rhythmicity but retained superficially normal ERGs under all conditions suggesting that circadian clocks are dispensable for general retinal function. However, clock loss was associated with subtle abnormalities in retinal responses, with the amplitude of cone and mixed rod + cone ERGs constitutively enhanced. These data suggest that circadian clocks drive a fundamental fine-tuning of retinal pathways that is particularly apparent under conditions in which vision relies upon either cones alone or mixed rod + cone photoreception.
Cameron
Morven A
MA
Faculty of Life Sciences, Michael Smith Building, University of Manchester, Manchester, UK.
Barnard
Alun R
AR
Hut
Roelof A
RA
Bonnefont
Xavier
X
van der Horst
Gijsbertus T J
GT
Hankins
Mark W
MW
Lucas
Robert J
RJ
D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology*; D055253:Color Vision / Q000235:genetics / Q000502:physiology*; D056931:Cryptochromes; D003623:Dark Adaptation / Q000502:physiology; D004596:Electroretinography; D005420:Flavoproteins / Q000235:genetics* / Q000502:physiology*; D007150:Immunohistochemistry; D055255:Mesopic Vision / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012160:Retina / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
C538964:Cry1 protein, mouse; C538967:Cry2 protein, mouse; D056931:Cryptochromes; D005420:Flavoproteins