Post-traumatic stress disorder (PTSD) is a psychiatric condition that can develop when people experience a stressful and life-threatening event. Clinical research indicates that the presence of a state of hyperarousal after a traumatic experience is the best predictor of a subsequent diagnosis of PTSD. The role of arousal peptides called orexins (hypocretins) in a PTSD-like condition produced by exposing rats to a single episode of footshocks (5× 2 s episodes of 1.5 mA) was investigated in this thesis. The first part of my thesis involves the characterization of the footshock model of PTSD and the second part examines the involvement of orexins in this footshock model. The following findings are reported. First, shock rats that exhibited a high level of anxiety to a novel tone (high responders, HR) the day after the footshock exposure subsequently displayed more avoidance when compared to shock rats that exhibited a low level of anxiety (low responders, LR). These results highlight the importance of individual differences in the reaction to a strong fear-inducing experience. Second, the orexin precursor peptide prepro-orexin (ppOX) mRNA was found to be elevated in rats at 6 and 14 days after exposure to footshocks. In addition, ppOX mRNA levels were found to be positively correlated with anxiety at 14 days post-shock. Third, pre-shock injections of the corticotropin releasing factor receptor antagonist antalarmin were found to attenuate the anxiety expressed to the shock chamber and eliminate the correlation between ppOX mRNA levels and anxiety. Fourth, systemic injections of the nonselective orexin receptor antagonist TCS-1102 was found to attenuate the anxiety expressed in rats at 14 days post-shock. Fifth, TCS-1102 was found to have anxiolytic effects that were specific for the HR. The results of these experiments provide evidence linking the orexin system to the anxiety produced by exposure of rats to footshocks. They also provide preclinical evidence in support of the use of orexin antagonists for the treatment of anxiety in PTSD.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:MWU.1993/22157 |
| Date | 08 1900 |
| Creators | Chen, Xiaoyu |
| Contributors | Kirouac, Gilbert J. (Oral Biology), Scott, J. Elliott (Oral Biology) Bergen, Hugo T. (Human Anatomy & Cell Science) Fry, Mark (Biological Sciences) Viau, Victor (University of British Columbia) |
| Publisher | Brain Structure and Function, Behavioral Brain Research |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Detected Language | English |
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