Cone function studied with flicker electroretinogram during progressive retinal degeneration in RCS rats

Area of Science:

• Neuroscience
• Ophthalmology
• Genetics

Background:

• The Royal College of Surgeons (RCS) rat exhibits inherited retinal degeneration, affecting retinal pigment epithelial cells.
• This defect leads to progressive photoreceptor loss, impacting central visual function.
• Cone degeneration occurs more slowly than rod loss, persisting anatomically up to two years of age.

Purpose of the Study:

• To investigate the impact of progressive retinal degeneration on cone function in RCS rats.
• To analyze age-related changes in cone electroretinogram (ERG) responses.

Main Methods:

• Electroretinograms (ERGs) were recorded in response to white light flashes in pigmented dystrophic and congenic non-dystrophic RCS rats.
• Frequencies ranged from 3 to 50 Hz under light-adapted conditions.
• Rats aged from 18 to 300 days were studied.

Main Results:

• Maximal ERG amplitudes were consistently observed at 3 Hz across all ages and groups.
• Response amplitude and critical fusion frequency increased from P18 to P21 in both groups.
• After P21, these parameters progressively declined with age in dystrophic rats, with prolonged latency and later phase shifts.
• ERG responses were detectable up to P200 in dystrophic rats, characterized by negative deflections.

Conclusions:

• Dystrophic RCS rats demonstrate a progressive decline in cone function with age.
• Cone system development appears normal up to P21, with comparable flicker responsiveness to non-dystrophic controls.
• The ERG findings up to P200 reflect the severe pathological state and altered retinal connectivity in this model.