Electronic Thesis and Dissertation Repository


Master of Science




Dr. Klaus-Peter Ossenkopp

2nd Supervisor

Dr. Martin Kavaliers

Joint Supervisor


This thesis examined the effects of neonatal acute immune activation with the endotoxin, lipopolysaccharide (LPS) on postnatal days 3 and 5 on adolescent anxiety-like behaviour in rats before and after a stress period. Previous research has shown that adults rats exposed to LPS during the neonatal stage show anxiety-like behaviour following a period of stress. This thesis investigated this effect in adolescence. The present results showed significantly higher anxiety-like behaviour in saline controls, and a potential neuroprotective effect of low dose LPS (15 µg/kg) contrary to what was reported in adult rats. As well, a phase of stressful, aversive conditioning (conditioned disgust) did not elicit anxiety-like behaviour in LPS-treated adolescent rats. The findings of this study provide novel findings about the adolescent period, and suggest the use of no injection controls for neonatal research. This thesis presents data that suggests the importance of no injection controls in future neonatal research involving. This thesis also provided support to previous literature investigating sex differences in anxiety-like behaviour; female adolescent rats showed less anxiety-like behaviour compared to male adolescent rats. Overall, endotoxin exposure did not appear to be a significant risk factor for the development of anxiety disorders in adolescence. Physical stress during the early-life period may be of importance when researching risk factors for anxiety disorders.