Behavioral analysis of basal anxiety and conditioned fear in the mouse strain C57BL/6J

Abstract

Fear conditioning has been used to study pathogenic mechanisms underlying anxiety disorders. Several studies have shown that humans with anxiety disorders exhibit strong fear responses during the acquisition of conditioned fear. However, there have been no studies investigating whether basal anxiety within the normal range is related to conditioned fear. We hypothesized that individual differences in conditioned fear are correlated to the basal anxiety level of each individual. To test this hypothesis, we measured the basal anxiety of mice by using the elevated-plus maze (EPM) and open field test (OFT) and correlated these data with contextual freezing during contextual fear conditioning (CFC). Strong correlation was found between the basal anxiety level measured in the OFT and contextual freezing in the CFC. Baseline freezing was also strongly correlated with the freezing level during the retrieval phase of CFC. However, the basal anxiety level measured in the EPM was correlated neither with conditioned fear nor with baseline freezing in the CFC. These results suggest that both basal anxiety in the OFT and baseline freezing are related to contextually conditioned fear.