Abstract
Purpose: :
To compare rod ERG photoresponses obtained from dark–adapted isolated mouse retinas by pharmacological isolation and by the paired–flash technique.
Methods: :
Rod photoresponses to 20 ms flashes (544 nm) were recorded by the ERG technique across isolated mouse retinas perfused with 1) Ringer’s solution, 2) Ringer’s solution including aspartate (eliminating the b–wave) and 3) Ringer’s solution including aspartate and barium (eliminating the slow PIII (glial) component). In the paired–flash technique the test flash (633 nm) photoresponses were derived by measuring the amplitude of the rod–saturating fixed intensity probe flash (544 nm) following the test flash at times t = tprobe + tmeas, where the measuring time tmeas was varied between 0.02s to 1s.
Results: :
The paired–flash method eliminated the b–wave and the slow PIII component. Still, the choice of tmeas appeared to affect the derived test flash response amplitude. The rod–saturating probe flash response contains a fast "nose" component that is reduced by the test flash, depending on the test flash intensity and the interval (tprobe) between flashes. As at different times of tmeas, different amounts of the nose component are present, the amplitude of the derived test flash photoresponse is dependent on tmeas. When tmeas was chosen at the plateau phase (after the nose) the derived test flash photoresponses coincided exactly with the "pure" rod photoresponses recorded in solution 3). The "error" brought by varying tmeas was up to 30 % of the response amplitude in solution 3). The kinetics of the derived response appeared to be unaffected regardless of the changes in the nose component.
Conclusions: :
The choice of the measuring time in the paired–flash technique may cause a significant error in the derived rod ERG response amplitude but it does not affect the derived photoresponse kinetics.
Keywords: electroretinography: non-clinical • photoreceptors • electrophysiology: non-clinical