Development of A method activating NF-κB by optogenetic stimulation for In Vivo conditions to examine the role of CNS inflammation in the pathophysiology of primary depression

One of the critical limitations of the studies examining the effects of neuro-inflammation on depression is not implementing a protocol compatible with the pathophysiology of primary depression instead of using a protocol that inflammation is triggered by a bacterial endotoxin such as lipopolysaccharide. In order to elucidate the complex relationship between neuro- inflammation and depression, it is necessary to develop a reliable model for neuro- inflammation originating from the brain. Based on this requirement, this thesis study was carried out in order to adapt a system with in vitro activity that triggers inflammation originating from the brain, similar to the inflammatory response triggered by stress in physiological conditions, to in vivo conditions. For this purpose CRY2PHR- DAI/CIB1-DAI cryptochrome receptors were transferred intrahippocampally with repeated plasmid injections and activated with repetitive optical stimulations. Plasmid injections and optical stimulation were performed with different protocols in order to determine the injection and optical stimulation dose and duration that would lead to optimal inflammation. However, an intense signal consistent with the mCherry signal was observed in the hippocampal region in the control groups that were not optically stimulated and were not injected with plasmid. It was evaluated that this may have arisen due to tissue trauma caused by repeated injection of the plasmid, and it was not possible to reliably determine the true signal within this signal intensity. In future studies, in order to minimize the inflammation caused by trauma due to interventional procedures, it is recommended to permanently express the plasmid by viruses instead of repetitive plasmid injections in methods to be developed to model inflammation in the brain, and to start optical stimulation 4-6 weeks after virus injection.