Abstract
1. A microtechnique allowing the study of single plasma membranes from the gamma-aminobutyric acid (GABA)-acceptive Deiters' neuron has been utilized in order to assess the effect of both S-100 protein and its antiserum on 36Cl- permeability through such membranes. 2. The results show that both S-100 (in the Ca2+ form) incorporation onto the external side of the membranes and their preincubation with anti-S-100 serum stimulate 36Cl- permeability. 3. These effects are not additive with that of GABA, indicating that both S-100 and anti-S-100 act via the GABAA receptor complexes on Deiters' membranes. 4. When the membranes were incubated first with S-100/Ca2+ and then with anti-S-100, the second treatment resulted in the disappearance of the S-100 effect. However, the anti-S-100 effect was fully displayed.