Fig. 2. Synaptic GABA^Areceptors discriminate between anesthetic and nonimmobilizer. (  A ) 36 μm F6 (> 2 × MAC^pred,  black trace ) had no effect on the decay of GABA^AmIPSCs. (  B ) By contrast, 100 μm isoflurane (0.3 × MAC,  black trace ) slowed the decay by approximately 30% (from 20 ms to 26 ms). (  C ) Summary of the effects of F6 and isoflurane on the decay time constants of GABA^AIPSCs. Isoflurane slowed IPSCs in a dose-dependent manner up to the highest concentrations tested, whereas F6 at similar MAC^predconcentrations had no effect. (Data for F6 based on recordings from 4 and 13 cells for sIPSCs and mIPSCs, respectively. Isoflurane data at 0.3 × MAC from 3 cells, other isoflurane concentrations taken from reference 8. Hill coefficient is 3.8 for isoflurane data.) GABA^A=γ-aminobutyric acid type A; IPSC =inhibitory postsynaptic current; MAC^pred=predicted minimal alveolar concentration; mIPSC =miniature inhibitory postsynaptic current; sIPSC =spontaneous inhibitory postsynaptic current.