title: Individual differences in novelty-seeking behavior in rats as a model for psychosocial stress-related mood disorders.
abstract: Most neuropsychiatric disorders, including stress-related mood disorders, are complex multi-parametric syndromes. Diagnoses are therefore hard to establish and current therapeutic strategies suffer from significant variability in effectiveness, making the understanding of inter-individual variations crucial to unveiling effective new treatments. In rats, such individual differences are observed during exposure to a novel environment, where individuals will exhibit either high or low locomotor activity and can thus be separated into high (HR) and low (LR) responders, respectively. In rodents, a long-lasting, psychosocial, stress-induced depressive state can be triggered by exposure to a social defeat procedure. We therefore analyzed the respective vulnerabilities of HR and LR animals to long-lasting, social defeat-induced behavioral alterations relevant to mood disorders. Two weeks after four daily consecutive social defeat exposures, HR animals exhibit higher anxiety levels, reduced body weight gain, sucrose preference, and a marked social avoidance. LR animals, however, remain unaffected. Moreover, while repeated social defeat exposure induces long-lasting contextual fear memory in both HR and LR animals, only HR individuals exhibit marked freezing behavior four weeks after a single social defeat. Combined, these findings highlight the critical involvement of inter-individual variations in novelty-seeking behavior in the vulnerability to stress-related mood disorders, and uncover a promising model for posttraumatic stress disorder.
authors.affiliation: Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306, USA.
authors.forename: Florian
authors.initials: F
authors.lastname: Duclot
authors.forename: Fiona
authors.initials: F
authors.lastname: Hollis
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Darcy
authors.forename: Mohamed
authors.initials: M
authors.lastname: Kabbaj
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning; D003214:Conditioning, Classical; D004195:Disease Models, Animal; D004291:Dominance-Subordination; D005106:Exploratory Behavior / Q000502:physiology*; D005239:Fear; D005260:Female; D005518:Food Preferences; D007206:Individuality; D008297:Male; D008568:Memory; D009043:Motor Activity / Q000502:physiology; D009919:Orchiectomy; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D013315:Stress, Psychological / Q000503:physiopathology*; D013395:Sucrose / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D013395:Sucrose