Fig. 3. Fear to context was measured as the percent of time a mouse froze in the presence of the environment in which the mouse had received three foot shocks on the preceding day. A greater percentage time spent freezing indicated greater remembrance. Increasing isoflurane concentration from 0 to 0.5% decreased freezing in a rectilinear manner. There was no difference by genotype in the capacity of isoflurane to interfere with fear to context as assessed by slope, intercept, or the effective concentration producing 50% of the maximal response (EC50) of the regression lines. For SL/SL (wild-type) mice, the slope was −90.4 ± 12.2 and the intercept was 50.3 ± 3.6 (n = 64). For SL/HA (heterozygous) mice, the slope and intercept (± SE) were −95.8 ± 11.6 and 48.2 ± 3.4 (n = 101 mice). For HA/HA (homozygous knock-in) mice, these values were −85.1 ± 15.0 and 41.6 ± 4.2 (n = 64). Data for genotypes are displaced slightly on the abscissa to decrease overlapping of error bars.
