Figure 2. A supraadditive interaction between midazolam and propofol was apparent when the concentration of [small gamma, Greek]-aminobutyric acid (GABA) was reduced to 0.3 [micro sign]M. (A) Responses evoked by 0.3 [micro sign]M GABA, GABA + 0.5 [micro sign]M midazolam, GABA + 1 [micro sign]M propofol, and GABA + propofol + midazolam were smaller than the currents evoked by a saturating concentration (600 [micro sign]M) of GABA. (B) The peak currents for each group were normalized to the peak GABA (0.3 [micro sign]M) current. The theoretical additive response was significantly less than the measured responses to midazolam and propofol (P < 0.05, Student's t test, n = 4).