Fig. 2. Experiment 1: Animals given 0% or 0.2% isoflurane and preexposure to 15 shocks in context A show enhanced fear conditioned to the single shock given in B compared with animals given these concentrations of isoflurane and 0 shocks in context A. Isoflurane concentrations of 0.4% and greater suppressed stress-enhanced fear learning. * Significant differences (  P < 0.05) between groups.