The Influence Of Endothelial Nitric Oxide Synthase Deficit On Sickness Behavior After Ischemic Stroke

Ischemic stroke, the acute severe cerebrovascular disease, remains the leading cause of disability in the world. Owing to obstacle of blood flow to the brain, it manifests rapid onset of neurologic injury. Sickness behavvior such as dementia, depression, anxiety and fatigue severly influence functional outcome after ischmic stroke. Also, the number of affected individuals continues asending in recent years. Despire the currency of pharmacological treatments in clinic, there is still restricted understanding of physiology and pathophysiology; therefore, the specific therapies for prevention or improvement are unknown.e NOS has been found to play a paramount role in neurological function and cognition. It is reported that e NOS-deficient(e NOS^-/-) mice display a reduction in motor-recovery after sroke. However, it is not clear if e NOS mediates the recovery of memory and behavior after stroke.In this study, we investigated hypothesis that deletion of e NOS inhibits the recovery of memory using e NOS knockout mice and rodent stroke model.Methods:1. Thitrty-four c57 BL/6 adult wild type（WT） and thirty-five e NOS^-/- mice were randomly divided into two groups, respectively. Different groups were subjected to either sham-operation or 60 minutes of transient middle cerebral artery occlusion（MCAO）.2. Functional outcomes include neurological score, limb asymmetry（cylinder test）, sensory motor function（adhesive removal test）, and spatial memory（Morris water maze test, MWM） were measured throughout the course of 4 weeks.3. Nissl staining was used to evaluate the damage to central nervous system. The level of microglia was measured using immunohistochemistry staining, while the expression of Interferon-γ（IFN-γ） was detected by enzyme-linked immuno sorbent assay（ELISA）.Results:1. The e NOS^-/- MCAO mice had longer time to complete the cylinder test during the first two weeks after stroke（p<0.05）.2. The e NOS^-/- MCAO mice had significantly higher number of non-performers compared to the WT MCAO mice during MWM（p=0.002）. The e NOS^-/- MCAO mice had significantly longer time to complete the spatial memory test of MWM compared to WT MCAO mice（p=0.004）.3. There were no significant differences in neurological score, adhesive removal test and lateralization index between the two groups at the third week after stroke when MWM testing was performed. It suggested that the decreased performance in MWM in e NOS^-/-MCAO mice was not associated with neurological or motor deficit.4. The number of microglia in the striatum on the lesion side was significantly higher than those on the normal side in WT MCAO（p=0.020）; however, such elevation was attenuated in e NOS^-/- MCAO mice（p=0.039）. Also, the production of IFN-γ was substantially decreased in e NOS^-/- mice compared to WT mice after stroke（p<0.001）.Conclusions:1. The data suggest that loss of e NOS results in spatial memory after stroke.2. Our data show that e NOS deficient mice after stroke developed more depression-like behavior.3. Our data suggest that accumulation of microglia in the lesion striatum after stroke wasattenuated in e NOS deficient mice.4. The data show that knock-out e NOS inhibit increasing productions of IFN-γ after stroke, which may get involved in inflammatory cascade.