Fig. 7.

The slow PIII response of the ERG in Kir4.1 +/+ and Kir4.1 −/− mice. Traces show the intraretinal ERG recorded between an electrode in the distal retina and one in the vitreous humor. In a Kir4.1 +/+ mouse, a transient negative b-wave and a slower positive slow PIII response are evident (+/+). When Ba²⁺ (0.4 mm) is added to the superfusate (+/+ plus Ba²⁺), the slow PIII response is abolished, whereas the b-wave remains primarily unchanged. Subtracting the trace in Ba²⁺from the other (+/+ difference) reveals the Ba²⁺-sensitive component of the ERG, the slow PIII response in isolation. In a Kir4.1 −/− mouse (−/−), the b-wave is present but the slow PIII response is absent. Addition of Ba²⁺ (−/− plus Ba²⁺) produces a small increase in the b-wave but no change in the response after decay of the b-wave, as illustrated by the differencetrace (−/− difference). The time course of the light stimulus is shown at the bottom.Dashed lines indicate prestimulus baseline levels.