Behavioural Brain Research 215 (2010) 95–101 Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Research report Behavioural habituation to novelty and brain area specific immediate early gene expression in female mice of two inbred strains Amber R. Salomons a,b,∗ , Glenn Bronkers a , Susanne Kirchhoff a,b , Saskia S. Arndt a,b , Frauke Ohl a,b a Department of Animals in Science and Society, Division of Animal Welfare and Laboratory Animal Science, Utrecht University, Utrecht, The Netherlands b Rudolf Magnus Institute of Neuroscience, Utrecht, The Netherlands article info Article history: Received 7 May 2010 Received in revised form 25 June 2010 Accepted 29 June 2010 Available online 6 July 2010 Keywords: Anxiety Habituation Modified hole board Female BALB/c mice Female 129P3/J mice c-Fos expression abstract In mice, emotional adaptation might be assessed by changes in behavioural responses towards novelty over time (i.e. habituation), with non-adaptive anxiety being expressed by a lack of habituation. Recently we found that male 129P3/J mice showed such a profound lack of habituation in comparison to male BALB/c mice. From these results we concluded that male 129P3/J mice might model non-adaptive, i.e. pathological anxiety. As a first step in the process of assessing the generalizability of our results, we inves- tigated whether these results were robust across gender. Therefore we replicated our previous study in female individuals. Results from the present study reveal behavioural habituation towards novelty, i.e. an adaptive phenotype in female BALB/c mice. In contrast, females of the 129P3/J strain were charac- terised by a lack of habituation, similar as their male counterparts. Compared to female BALB/c, female 129P3/J mice showed lower neural activity in brain areas known to regulate the integration of emotional and cognitive processes. Extending the results found in males, female 129P3/J mice revealed increased post-testing plasma corticosterone levels and higher neural activity in brain areas related to emotional processing than females of the BALB/c strain. Taken together our results demonstrate that both gen- ders of the 129P3/J mouse strain are characterised by a non-adaptive anxiety phenotype, strengthening the hypothesis that the 129P3/J strain may be a promising (neuro)-behavioural model for pathological anxiety. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Anxiety disorders are amongst the most prevalent types of psy- chiatric disorders and affect about 10–17% percent of the world population [20,37]. Commonly used animal models of anxiety are based on the exposure of animals to novel stimuli, induc- ing biologically adaptive avoidance behaviour, i.e. normal anxiety. An appropriate animal model for pathological anxiety in con- trast should mirror a biological non-adaptive, i.e. pathological response [27]. Furthermore, characteristics of pathological anxiety should be detectable in both genders of a potential animal model [39]. One procedure to differentiate between normal and patholog- ical anxiety may be the evaluation of behavioural habituation to ∗ Corresponding author at: Division of Animal Welfare and Laboratory Animal Sci- ence, Department of Animals in Science and Society, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, P.O. Box 80.166, 3508 TD Utrecht, The Netherlands. Tel.: +31 0302534149; fax: +31 0302537997. E-mail address: a.r.salomons@uu.nl (A.R. Salomons). a given stimulus over time. Non-adaptive anxiety would then be mirrored by a lack of habituation [35]. Recently we found that male 129P3/J mice are characterised by such a lack of habituation and under more aversive experimental conditions even reveal sensitisation [35]. In contrast, for example male BALB/c mice which have been reported to be highly anxious [4,5,17,22,35] show rapid habituation to the same test environ- ment [35], a phenomenon which has been reported for other inbred rodent strains used as models for anxiety as well [29,30]. In addition to their behavioural characteristics, distinct brain areas (e.g. prelimbic cortex and lateral septum) in 129P3/J male mice compared to rapidly habituating BALB/c male mice revealed a lower c-Fos expression after the habituation procedure [35]. This finding suggests that individuals from the 129P3/J strain may be impaired in correctly integrating information about their environ- ment and emotional processes, a prerequisite to adapt behavioural responses over time. From these results we concluded that male 129P3/J mice might be an interesting animal model for pathological anxiety. As a first step in the process of assessing the generalizability (external validity) of our results, we investigated whether these 0166-4328/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2010.06.035