Calcium-activated chloride channels in Müller cells acutely isolated from tiger salamander retina

Ca²⁺-activated chloride channels were identified with whole-cell patch-clamp recording techniques in salamander retinal Müller cells. Cl(Ca) channels were activated by membrane depolarizations that elicited Ca ²⁺ influx or the application of the Ca²⁺ ionophore, ionomycin. The Ca channel blocker, Cd²⁺, abolished the Cl(Ca) channel tail currents. Increasing the duration of the depolarizing pulse resulted in enhancement of the Cl(Ca) channel tail current. Repetitive depolarizations with rapid pulses to +20 mV produced a buildup of I_Cl(Ca), which reversed at 0 mV in symmetrical [Cl^-] and at -40 mV when intracellular [Cl^-] was reduced to 10% of the external concentration. I _Cl(Ca) was blocked by the Cl channel blocker niflumic acid, while niflumic acid had no effect on voltage-gated Ca channels. These results offer the first demonstration of Cl(Ca) channels in a nonastrocytic glial cell and expand our understanding of the functional capacities of retinal glial cells.