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. 2007 Mar 16;90(4):674-81.
doi: 10.1016/j.physbeh.2006.12.006. Epub 2006 Dec 28.

The delayed effects of chronic unpredictable stress on anxiety measures

Leslie Matuszewich  1 , Jared J Karney, Samantha R Carter, Steven P Janasik, Johanna L O'Brien, Ross D Friedman
Affiliations

The delayed effects of chronic unpredictable stress on anxiety measures

Leslie Matuszewich et al. Physiol Behav. .

Abstract

Previous research has found that exposure to unpredictable stress can augment anxiety in humans and animals. The appearance of anxiety symptoms in humans frequently develop after stress exposure has terminated, but few rodent studies have systematically examined the delayed anxiogenic effects of unpredictable stress. Therefore, the current study investigated whether anxiety-like behaviors in rats would increase at several time intervals following exposure to chronic unpredictable stress (CUS). Unconditioned and conditioned response tasks were used to assess anxiety in male rats 1, 7 or 14 days following exposure to 10 days of a variety of stressors. Rats exposed to CUS showed increased burying behaviors and immobility during the defensive burying test, a conditioned anxiety test. The effects on burying behavior were apparent 7 and 14 days after the termination of the unpredictable stress procedure, but not when tested 1 day after CUS. Total time immobile in the defensive burying test also increased 14 days after termination of the last stressor. In contrast, there were no significant effects of CUS on behavioral measures in the unconditioned response tasks, the elevated plus-maze or light-dark box, at any time point following exposure to CUS. The current findings suggest that CUS may be a useful model of human conditioned anxiety that develops subsequent to chronic stress exposure.

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Figures

Fig 1
Fig 1
Exposure to CUS increased anxiety measures in the defensive burying task. Rats exposed to CUS and tested 7 or 14 days later demonstrated increased burying behaviors as indicated by the height of the bedding pile (top panel) and the duration of burying behavior in the 15 min test (bottom panel). Bars represent mean ± SEM. * indicates a significant difference from non-stressed control group (p<.05), + indicates a significant different from CUS rats tested 1 day after stress ended (p<.05).
Fig. 2
Fig. 2
Exposure to CUS altered the latency to initiate burying in the defensive burying task. The rats exposed to CUS and tested 1 day later initiated burying faster than non-stressed controls (top panel). There were no differences in the time to initiate shock between groups (bottom panel). Bars represent mean ± SEM. * indicates a significant difference from non-stressed control group (p<.05), + indicates a significant different from CUS rats tested 1 day after stress ended (p<.05).
Fig. 3
Fig. 3
Exposure to CUS altered immobility measures in the defensive burying task. Rats exposed to CUS and tested 14 days later showed increased immobility behavior as indicated by the duration of immobility in the 15 min test (top panel) and the frequency of immobility episodes (bottom panel). Bars represent mean ± SEM. * indicates a significant difference from non-stressed control group (p<.05), + indicates a significant different from CUS rats tested 1 or 7 days after stress ended (p<.05).
Fig. 4
Fig. 4
Exposure to CUS decreased body weight gain. During the stress exposure (days 2-11), CUS rats gained less weight over time than non-stressed control rats. Symbols represent mean + SEM. Each arrow indicates when behavioral tests were conducted. The 1st arrow also indicates the end of the CUS procedure for all stressed rats.
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