Individual differences in novelty-seeking behavior in rats as a model for psychosocial stress-related mood disorders

Physiol Behav. 2011 Aug 3;104(2):296-305. doi: 10.1016/j.physbeh.2010.12.014. Epub 2010 Dec 21.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Avoidance Learning
  • Conditioning, Classical
  • Disease Models, Animal
  • Dominance-Subordination
  • Exploratory Behavior / physiology*
  • Fear
  • Female
  • Food Preferences
  • Individuality*
  • Male
  • Memory
  • Motor Activity / physiology
  • Orchiectomy
  • Rats
  • Rats, Long-Evans
  • Rats, Sprague-Dawley
  • Stress, Psychological / physiopathology*
  • Sucrose / administration & dosage
  • Time Factors


  • Sucrose