Fig. 9.

Equi-effective concentrations of modulators at a low taurine concentration also have equal efficacy at a saturating taurine concentration. A, sample tracing showing how the concentrations of toluene and isoflurane that yield an ∼200% potentiating effect of EC_5–10 taurine were determined. The tracing shows the effect of EC_5–10 taurine with and without several concentrations of isoflurane or toluene. Toluene (0.42 mM) potentiated EC_5–10 taurine ∼200%, whereas 0.55 mM isoflurane potentiated to a higher degree, and 0.28 mM isoflurane produced ∼200% potentiation of EC_5–10 taurine. EC_5–10 taurine applications preceded and followed each coapplication with a modulator. Horizontal bars above tracings indicate the times of exposure to taurine, toluene, or isoflurane at the concentrations indicated. B, sample tracing demonstrating the enhancing effects of the toluene and isoflurane concentrations found in A to produce ∼200% potentiation of taurine-mediated currents, but this time applied with a saturating concentration (EC₁₀₀) of taurine. Coapplications of taurine and modulator were preceded and followed by applications of EC₁₀₀ taurine alone. C, summary of the effects of EC₁₀₀ taurine plus 0.42 mM toluene or 0.28 mM isoflurane. The y-axis represents the percentage increase in current observed in the presence of modulator compared with that produced by taurine alone. Data are shown as mean ± S.E.M. of four oocytes.