Figure 6.

An increase in the GluN2A/GluN2B ratio before fear learning impairs LTM consolidation. A, Behavior timeline for fear learning experiment. Wild-type, α-CaMKII-tTA+, GFP-GluN2A+, and GFP-GluN2A+/tTA+ mice were maintained on Dox, Dox was removed from their diet for 14 d, and then the mice were fear conditioned with three TSPs. Three hours after training, the mice conditioned fear responses to the auditory cue were examined in an STM test in which the mice were exposed to three tones. Twenty-one hours later, LTM was examined where the mice were exposed to five tones. B, For STM, there was no significant main effect of genotype on percentage freezing (wild-type, α-CaMKII-tTA+, GFP-GluN2A+, or GFP-GluN2A+/tTA+). C, For LTM, there was a significant main effect of genotype on percentage freezing. The GFP-GluN2A+/tTA+ group froze significantly less compared with the wild-type, α-CaMKII-tTA+, and GFP-GluN2A+ groups. However, there were no differences in percentage freezing among the wild-type, α-CaMKII-tTA, and GFP-GluN2A+ groups (wild-type vs α-CaMKII-tTA, α-CaMKII-tTA vs GFP-GluN2A+, GFP-GluN2A+ vs wild-type (*p < 0.05). Error bars indicate SEM.