Calcium- and voltage-dependent potassium channel in the rat retinal amacrine cells identified in vitro using a cell type-specific monoclonal antibody.

Single-channel currents were studied from identified amacrine cells of rat retinal monolayer cultures. Cells were immunohistochemically identified using an amacrine cell-specific monoclonal antibody, HPC-1. Single-channel currents with the following properties were observed. (1) The mean opening duration was voltage dependent, tending to increase on hyperpolarization. (2) The reversal potential was almost identical to the calculated EK derived from the potassium concentration gradient. (3) The conductance was 110 pS at a low extracellular potassium concentration. (4) Currents were blocked by TEA. (5) Mean opening duration was also dependent on the calcium concentration of the intracellular side. These properties were consistent with the voltage and calcium-dependent potassium channels of a large conductance. Our results also demonstrated that cell-type-specific monoclonal antibodies together with electrophysiological recordings offer a very useful method to investigate the physiological properties of distinct neuronal types in mixed cell cultures.