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Recovery of the rod photoresponse in infants
Ronald M Hansen1, Anne B Fulton
1Department of Ophthalmology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. ronald.hansen@childrens.harvard.edu
Insights
Rod photoresponse deactivation is slower in infants compared to adults. This slower deactivation, measured by recovery time, may be influenced by the amount of rhodopsin present in developing infant eyes.
Area of Science:
- Ophthalmology
- Developmental Biology
- Phototransduction
Background:
- Rod photoreceptor development involves increasing rhodopsin content.
- Rhodopsin influences rod phototransduction activation parameters.
- Kinetics of rod photoresponse deactivation in infants are not well understood.
Purpose of the Study:
- Investigate the deactivation kinetics of the rod photoresponse in infants.
- Utilize a paired-flash electroretinography (ERG) procedure.
- Compare infant rod response recovery to adult controls.
Main Methods:
- Measured rod-isolated a-wave amplitudes using ERG in response to paired flashes.
- Assessed recovery in 4- and 10-week-old infants and adults.
- Determined the time to half-maximal recovery (t(50)) after a test flash.
Main Results:
- Infant rod response recovery time (t(50)) was significantly longer than in adults.
- The recovery function's shape remained consistent across age groups.
- t(50) values showed an inverse relationship with parameters of rod phototransduction activation.
Conclusions:
- Rod photoresponse deactivation kinetics are slower in infants.
- The proportion of isomerized rhodopsin may dictate deactivation kinetics in infants.
- Findings provide insights into visual system development and function in early life.
Purpose:
To study deactivation of the rod photoresponse in infants using a paired-flash procedure. Rhodopsin content increases and scales the parameters of the activation of rod phototransduction as rods develop. However, little is known about the kinetics of deactivation in the rods of young infants.
Methods:
ERG responses to pairs of flashes were used to study the recovery of the rod response in 4- and 10-week-old infants and mature control subjects. The amplitudes of rod isolated a-wave responses to a probe flash (+3.3 log scot td . s) presented 2 to 120 seconds after an equal-intensity test flash were measured. The interstimulus interval (ISI) at which the amplitude was half that of the response to the probe flash alone (t(50)) was determined by linear interpolation.
Results:
Recovery time (t(50)) was significantly longer in infants than in adults (F = 18.9, df 2, 32; P < 0.01). The shape of the recovery function did not vary with age. The t(50) values were inversely proportional to the parameters of activation of rod phototransduction.
Conclusions:
These results are evidence that the kinetics of deactivation in infants are slower and may be set by the proportion of rhodopsin isomerized.
