Experiment 2: Social Defeat Stress Followed by Porsolt Swim Testing

 Exposure to chronic social defeat stress (C/A) produced a significant increase in

total immobility time during the 15-min forced swim when compared with the immobility

times for the control rats that were not exposed to social defeat stress (NC/NA) (F (2, 21)

= 5.363, p < 0.0131; Fig. 3-9). When the data were analyzed in 5-min bins, there was a

significant between-groups effect as well as a significant time effect (F (2, 42) = 2.424, p

< 0.0150; F (2, 42) = 72.74, p < 0.0001; Fig. 3-10), but no significant group by time

interaction effect (F (4, 42) = 1.270, p < 0.2970; Fig. 3-10).

 Inter-Observer Reliability

 The two observer's recordings of total time freezing for the social defeat sessions

from Experiments la and lb combined differed by less than 20 sec for 94% of the

sessions and never differed by more than 28 sec. The two observer's recordings of

exploratory locomotion during social defeat sessions were identical in 70% of the

sessions and never differed by more than 3 lines crossed.

 The two observer's recordings of total immobility time during the Porsolt swim test

differed by less than 40 sec in 92% of the sessions and never differed by more than 43 sec.