Abstract
Purpose: :
To compare the a- and b-wave parameters of dark-adapted rod photoresponses recorded from anaesthesized mouse and from isolated mouse retinas.
Methods: :
Dark-adapted full-field DC-ERGs were recorded from anesthetized (6 mgkg-1 xylazine and 60 mgkg-1 ketamine) mice (C57Bl/6) and across isolated retinas from the same animals at 37 oC. Isolated retinas were perfused (~4 ml/min.) with bicarbonate-buffered Ringer’s solution from photoreceptor side. The photoisomerizations/rod in in vivo recordings were calculated as in Lyubarsky et al. (2004)1 and in transretinal ERG as in Heikkinen et al. (2008)2.
Results: :
The average a-wave time-to-peak (tp) recorded in vivo varied from 28 ms (40 Rh*) to 7 ms (60 000 Rh*), while in the isolated retina the corresponding values were from around 37 ms to 17 ms. The b-wave tp to the same stimuli varied from 50 to 30 ms in vivo and from 145 to 110 ms in the isolated retina. The a-wave maximum amplitude in vivo was typically around 0.5 mV, while the b-wave amplitude was about 1 mV. After isolation of the retina, the a-wave amplitude was typically slightly larger than in vivo, while the b-wave amplitude was approximately halved.
Conclusions: :
The rising phase of the a-wave appeared very similar in vivo and in the isolated retina. The b-wave kinetics was retarded and the amplitude was decreased in the isolated retina compared to that in vivo, which can explain the minor increase in both the a-wave amplitude and tp after the isolation of the retina.1Lyubarsky A., Daniele L., Pugh E. (2004), Vis. Research, 44(28):3235-512 Heikkinen H., Nymark S., Koskelainen A. (2008), Vis. Research, 48(2):264-72
Keywords: retina • electrophysiology: non-clinical • electroretinography: non-clinical