Acute recombinant apoE isoform application recapitulates alterations in LTP induction. Application of 100 nM recombinant human apoE isoforms 5 min prior to start of recording. A) Paired pulse facilitation. Second stimuli delivered at 20 ms intervals from 20 to 300 ms from first stimuli. Percent facilitation of fEPSP slope of second response as percentage of first response. B) Long-term potentiation induced by 5 trains of theta-burst stimulation (arrow). Expressed as slope of fEPSP, standardized to the first 20 minutes of recording. C) Average potentiation of last 20 minutes of recording. control = black circle, n = 8; rhapoE2 = blue square n = 8; rhapoE3 = purple inverted triangle, n = 7; rhapoE4 = red triangle, n = 6. Data expressed as mean ± SEM. *p < 0.05, ANOVA with Bonferroni's posttest.