Behavioural and neurobiological consequences of 2 different chronic stressors in rats

Background/aim: To compare the behavioural and neurobiological consequences of chronic headache and chronic mild stress (CMS) in rats. Materials and methods: Forty-eight male Wistar rats were divided into 4 groups: 1) control group, 2) chronic headache group, 3) CMS group, and 4) sham group. Their behaviour prior to (D0) and after (D14) chronic stress was analysed. Afterwards, they were exposed to the Elevated Plus Maze (EPM) in order to evaluate anxiety-like behaviour and the Forced Swim Test (FST) for observation of depressivelike behaviour. Ultrasonic vocalisations (USVs) were recorded by a USV detector system at D0 and D14 and during the FST. The c-fos expressions in various brain regions were analysed 2 h after the EPM and FST. Results: The control group showed significantly more sleeping behaviour at D14 (χ² = 8.213, P = 0.042), emitted more negative and positive affect USVs at D14 (χ² = 9.853, P = 0.020) and during FST (χ² = 4.000, P = 0.046) than the chronic headache and CMS groups, and showed significantly less anxiety-like behaviour in the EPM than the CMS group (P = 0.021). Conclusion: These results suggest that CMS increases anxiety-like behaviour but not depressive-like behaviour, while chronic headache does not have a significant effect on these behaviours in rats.