Fig. 3. Irreversible effects of photo-activated azi-etomidate on γ-aminobutyric acid type A (GABAA) receptors expressed in a single human embryonic kidney cell. ( A–D ) Current traces recorded from a single HEK293 cell expressing GABAAreceptors. ( A ) GABA currents recorded before treatment. GABA concentration is labeled in micromolar, and the bar over the traces indicates drug application. The ratio of peak currents at 10 μm versus 1 mm GABA, I10/I1000= 0.16; Deactivation τw(weighted average time constant) = 60 ms. ( B ) GABA currents recorded after 5 min cell treatment (on the microscope stage) with 3.2 μm azi-etomidate + 10 μm GABA + 365 nm light followed by 10-min wash. I10/I1000= 0.29; Deactivation τw= 590 ms. Maximal GABA current (I1000) is significantly reduced after treatment (Ipost/Ipre= 0.42). ( C ) Current elicited with 100 μm propofol before treatment. The maximal current normalized to the 1 mm GABA current in A is 0.41. ( D ) Current elicited with 100 μm propofol after treatment with azi-etomidate. The maximal current normalized to the 1 mm GABA current in B is 0.85. ( E ) Summary of I10/I1000results from cells treated on the microscope stage. Treatment conditions are indicated below the bars (as given in fig. 2 , and azi-etomidate concentrations are indicated in micromolar) and number of cells inside the bars . Deactivation τwdata show similar effects. * Differs from ECF control at P < 0.05.