Fig. 2. Effect of etomidate on learning and memory, as assessed by contextual fear conditioning. ( A ) Etomidate administered by intraperitoneal injection 30 min before the training session resulted in a dose-dependent reduction of freezing to context (ED50: 11 ± 0.1 mg). ( B ) Etomidate-induced learning impairment plotted as a function of the brain etomidate concentration ( lower axis ) and corresponding artificial cerebrospinal fluid (ACSF) concentration ( upper axis ).