2.2 Group sizes
The current experiment followed the rules for replacement, refinement, and reduction. Efforts were made to minimise suffering and reduce the number of animals used in the present study. The sample sizes were determined based on previous experience and reports of PCP-induced cognitive deficits in conditioned response tests (J. David Jentsch & Taylor, 2001). In total, 64 rats were randomly divided into four groups. The drug treatment regimen and the experimental protocol are shown in Figure 1. We used 32 rats for the Morris water maze test (n=8 per group) and 32 rats for the fear conditioning test (n=8 per group). Two rats were excluded because they died on the first and fourth days of PCP treatment, respectively.