Further evidence for the presence of gamma-aminobutyric acidA (GABAA) receptors on the cytoplasmic side of Deiters' membrane.

1. The permeation of labeled Cl- across single nerve membranes microdissected from rabbit Deiters' neurons was studied in a microchamber system. The in----out permeation of the ions was evaluated under control conditions and in the presence of either 10(-6) M GABA or 10(-6) M GABA plus 10(-5) M bicuculline methiodide (BMI) on the membrane cytoplasmic side. 2. In 32 experiments, involving one animal each, at least two membranes served as controls and at least two others were studied with the addition of GABA. Within each experiment all the membranes were obtained from the same animal. 3. In an additional 10 experiments, involving one animal each, at least two membranes served as controls and at least two others were studied in the presence of GABA plus bicuculline methiodide on the membrane cytoplasmic side. 4. The data show that 10(-6) M GABA on the Deiters' membrane cytoplasmic side stimulates Cl- permeation in----out by 42% (P = 0.0000001). When 10(-5) M BMI was present together with GABA, no stimulation of Cl- in----out permeation occurred.