Figure 3. Isoflurane and halothane produced a concentration-dependent depression of excitatory postsynaptic potential amplitudes. The concentration-response curves did not superimpose when plotted on a log minimum alveolar concentration axis, indicating that the two anesthetics were not equipotent at depressing glutamate-mediated excitatory synaptic transmission. Isoflurane (EC⁵⁰= 0.71 minimum alveolar concentration) was approximately 1.5 times more potent than halothane (EC⁵⁰= 1.1 minimum alveolar concentration), but both agents produced comparable depression of excitatory postsynaptic potentials over the clinically relevant range (0.5–2.0 minimum alveolar concentration). Each point represents the mean +/- SD from at least eight determinations.