3.2 Fingolimod attenuated PCP-induced contextual and tone memory retention deficits in rats in the fear conditioning task
Next, we used a contextual fear conditioning task to evaluate the effects of fingolimod on memory retention. A timeline of the experiment is presented in Figure 3A. The rats were subjected to consecutive tone-shock pairings in a conditioning training session and tested for contextual and tone-cued fear conditioning tests 24 and 48 h later, respectively. We found that the percentage of freezing time for the PCP-treated (10 mg/kg, i.p.) rats was significantly lower than that for the control rats, indicating impairments in fear memory retention. Fingolimod treatment (0.5 mg/kg, 1 mg/kg, i.p.) significantly increased the freezing time in a dose-dependent manner (Figure 3B). Similar effects were observed in the auditory-cued fear conditioning test, although they were not statistically significant. The decreased freezing time in PCP-treated rats was partially restored by fingolimod treatment (0.5 mg/kg, 1 mg/kg, i.p.) (Figure 3C). These results suggest that fingolimod attenuates PCP-induced deficits in fear memory retention.