Fig. 4.

Summary of the effects of 100 μmMTSET on glycine-activated currents in the WT and cysteine-substituted mutant GlyRs. MTSET was applied for a sufficient time for the current change to reach a steady-state value or for a period of 1 min, whichever came first. The percentage change was calculated as (I_{glycine,after}/I_{glycine,before}− 1) × 100. Light-shaded columns show the effect of MTSET when applied in the absence of glycine. Dark-shaded columns show the effect of MTSET when applied simultaneously with glycine. All points were averaged from three to nine different cells, and error bars (± SEM) are shown. The glycine concentrations (together with the approximate EC value) that were used in these experiments are as follows: WT, 20 μm(EC₅₀); R271C, 1 mm(EC₂₀); A272C, 1 mm(EC₂₀); S273C, 20 μm(EC₂₀); L274C, 200 μm(EC₂₀); P275C, 1 mm(EC₅₀); K276C, 1 mm(EC₂₀); V277C, 1 mm(EC₅₀); S278C, 100 μm(EC₅₀); Y279C, 1 mm(EC₂₀); V280C, 1 μm(EC₂₀); K281C, 20 μm(EC₂₀). Using a one-way ANOVA and Student–Newman–Keuls post hoc test, we found that MTSET caused highly significant (p < 0.01) changes in current magnitude in the R271C, A272C, S273C, L274C, P275C, and K276C mutant GlyRs, relative to the C41A mutant GlyR. However, the magnitude of the current change was not significantly dependent on whether MTSET was applied in the open or closed state.