An electrogenic ionic pump derived from an ionotropic receptor: assessment of a candidate.

1. Data obtained studying permeability characteristics of single Deiters' membranes in a microchamber system show that intracellular GABA can activate chloride in-->out passage with a GABAA pharmacology. 2. The overall data suggest the presence of a chloride extrusion pump in these neurons based on intracellular GABA activated chloride channels. 3. This conclusion takes up a previous theoretical suggestion that ionic channels could work as ionic pumps provided an energy input modifies the energy profile along the permeation path. 4. According to our quantitative evaluation, this pumping mechanism works with a low yield and along a cycle with a strongly asymmetric behavior, being far from equilibrium due to powerful "leakage" pathways for chloride in these neurons.