Fig. 1.

Experimental procedures. Balb/cJ litters were assigned to 1 of 3 neonatal conditions, which occurred daily (8–11:00 am) between pnd 1 and 14: (1) 180-min of maternal separation (180-min MS), (2) 15 min of maternal separation (15-min MS), or (3) undisturbed (Control). Pups were weaned on pnd 21 and housed with same-sex litter mates. To evaluate the long-term effects of maternal separation on reactivity to mild stress, plasma CORT responses to mild handling stress were assessed before infection on pnd 24. Prior to infection, behavioral scores and body weights were assessed on pnd 26, while open field exploratory behavior was assessed on pnd 27. On pnd 28, all mice were intracranially inoculated with 5 × 10⁴ pfu of the BeAn strain of Theiler's virus (TMEV) (day 0 pi). The impact of maternal separation on the CORT response to TMEV infection was assessed on day 1 pi. In Experiment 1, behavioral scores and body weights were assessed every 3–6 days until day 14 pi. These mice were sacrificed at days 14, 21, and 35 pi for CNS viral titer plaque assays and tissue weights. The number of mice in each group is as follows: Control (day 14 n = 24, day 21 n = 23, day 35 n = 18), 15 min MS (day 14 n = 19, day 21 n = 19, day 35 n = 21) and 180 min MS (day 14 n = 26, day 21 n = 20, day 35 n = 18). Experiment 2, behavioral scores and body weights were collected every 2–5 days pi until day 24 pi. The number of mice in each group is as follows: Control n = 38, 15 min MS n = 60, and 180 min MS n = 38