Selective actions of barium on the c-wave and slow negative potential of the rabbit eye.

The c-wave and slow negative potential (incorporating the slow P111) are both thought to be generated by light-evoked changes in the concentration of potassium surrounding the photoreceptors. We find the intravitreal barium, a blocker of potassium conductance, eliminates the c-wave from the intact rabbit eye but not the slow negative response. However, if the pigment epithelium is damaged by systemic administration of sodium iodate, barium then eliminates the slow negative response.