Post-ischemia depression (PID) is a condition that affects approximately 30% of survivors from stroke or cardiac arrest and has an important impact on patients’ quality of life. Previous studies support important roles of the endocannabinoid (eCB) system in depression and brain ischemia. This study attempts to link all three variables together by investigating the role and mechanism of eCB signaling in the development of PID. A global ischemia + hypotension model was used to induce a PID phenotype in CD1 mice. Three ischemic time frames were tested, and even though all three could induce significant cell death in the CA1 region of the hippocampus, only the 15-minute time point led to an increased immobility time on the forced swimming test (FST). The main goal of this study was to investigate the effect of a cannabinoid type-I receptor (CB1R) antagonist/inverse agonist, AM281, on the development of two depressive symptoms: anhedonia, measured with the sucrose preference test (SPT), and behavioral despair, measured with the FST. AM281 administration was able to significantly reduce the symptoms of anhedonia and behavioural despair. Subsequently, the mechanism behind this antidepressant-like effect was investigated. Administration of bicuculine with AM281 did not significantly affect the antidepressant effect on the FST, therefore suggesting that AM281 does not act on GABAergic synapses. A similar protocol was adopted with NVP-AM077, where its administration combined with AM281 was able to block the effect of AM281, thus confirming the importance of glutamatergic synapses for the antidepressant effect of AM281. Furthermore, the administration of a TAT-GLUR2 peptide did not significantly affect the effect of AM281, implying that the astroglial cell-mediated LTD (long-term depression) at glutamatergic synapses is not involved in the antidepressant effects of AM281. Finally, a bilateral intra-BLA (basolateral nucleus of the amygdala) administration of AM281 was able to reduce the immobility time on the FST. In conclusion, these results highlight the important contribution of BLA glutamatergic synapses to the antidepressant-like effect conferred by AM281.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/35056 |
| Date | January 2016 |
| Creators | Bonneville, Marika |
| Contributors | Zhang, Xia |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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