Here we describe a sustained outward potassium current (IK) in retinal horizontal cells (HCs). IK is unusually small over the range of membrane potentials normally experienced by these cells, which are chronically depolarized. We hypothesize that this unique IK will reduce the amount of neurotransmitter required to shift the cell's membrane potential over a wide range, and will minimize the redistribution of potassium ions across the post-synaptic membrane when the cell is depolarized.