Figure 2.

The rat eyecup preparation improves the postbleach recovery of rod/cone-mediated ipRGC light responses. In this experiment, an intensity series (8.6–12.8 log quanta cm⁻² s⁻¹) of 10 s light steps was presented three times to every ipRGC, first during the dark-adapted state, then ∼10 min after the presentation of a 1 min 13.8 log quanta cm⁻² s⁻¹ light to bleach rod/cone photopigments, and finally ∼4 h after this bleaching light. These plots are averages of all the ipRGCs tested, with each cell's highest-amplitude light response normalized to 1. For the ipRGCs in isolated retinas (n = 9; left), their responses recorded 10 min after the bleach were somewhat larger those obtained ∼4 h later, indicating not only a lack of rod/cone photopigment regeneration but also a gradual rundown between these time points. By contrast, the light responses of ipRGCs in eyecups (n = 9; right) increased during these two time points, suggesting the RPE enabled some degree of photopigment regeneration during dark adaptation.