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S. Côté, C. Beaulieu, M. Dumont, P. Lachapelle; Photostasis Modifies Cone and Rod Responses in Rats . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5694.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The photostasis effect identifies the adaptative phenomenon that enables the retina to adjust structurally and functionally to its luminous environment. We examined, in albino rats, if the latter could be evidence with cone and rod mediated functions as measured with the electroretinogram. Methods: Adult female Sprague–Dawley rats were adapted to a 1–lux luminous environment (12 hour cycle) for 14 consecutive days, following which cone (intensity: 0,9 log cd.sec.m–2 with a background : 30cdm–2) and rod (12h of dark adaptation, intensity:–6,3 to 0,9 log cd.sec.m–2) ERGs were obtained (ERG1). Rats were then placed in a 300–lux environment for another14 days, at the end of which ERG2 session took place. Rats were then returned to the 1–lux environment again for another 14 days at the conclusion of which ERG3 session was conducted. Results: Compared to ERG1, rod responses in ERG2 were reduced by 36% (426±166µV vs269±56µV; p<0.05), while rod responses at ERG3 session were not different from ERG1 (426±166µV vs 422±69µV; p>0.05). Similarly, compared to ERG1, cone function in ERG2 was markedly but not significantly decreased by 34 % (186±54µVvs122±27µV; p>0.05) while at ERG3 session cone function was not different from that measured at ERG1 (161±49µVvs186±54µV; p>0.05). Conclusions: Our results confirm the existence of a photostasis effect in albino rats, as demonstrated with the full–field ERG. Our results would thus suggest that the photostasis phenomenon is a pan–retinal effect modifying rod and cone mediated functions almost similarly, albeit not at a significant level for cone mediated signals.
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