Acute effect of surgery and phenotype on hippocampal-dependent memory. After pre-operative training in a trace-fear conditioning paradigm, the percent time that a rat spent freezing during a 5 min epoch was assessed on postoperative day 7 when placed in the same context as the training. Data were analyzed with two-way ANOVA with post hoc pairwise t test comparisons with Bonferroni correction and results are expressed as mean and SD (n = 6). A significant interaction was noted between strain and surgery (P = 0.02). Post hoc pairwise comparison revealed that each of the surgical groups exhibited significantly less freezing time than their own sham cohort HCR; furthermore, the LCR surgical group exhibited significantly less freezing time than the HCR surgical group. There was no significant difference between the LCR/sham and HCR/sham groups. * P < 0.01. HCR = high capacity runner phenotype; LCR = low capacity runner phenotype; surg = surgery.