A Study On The Relationships Between Glial Gap Junctional Communication And Hippocampus Damage Following Focal Cerebral Ischemia

Objective Previous studies showed that delayed neuronal death was found in hippocampus after middle carotid artery occlution. In nervous system, astrocytes are coupled extensively by gap junctions, which are highly conductive channels that allow the direct transfer of intracellular messengers between interconnected cells. In this study, we investigated the effect of blocking gap junction communication after focal cerebral ischemia on delayed neuronal death in ipsilateral hippocampus.Methods Rats were divided into 3 groups, including sham group, MCAO group and MCAO+CBX group, randomly. A rat model of middle cerebral artery occlusion (MCAO) was made by the intralu minal occlusion technique. Carbenoxolone, a gap junction blocker, was only injected into the lateral ventricle of the rats in MCAO+CBX group. Behavior test were carried out 24h after ischemia.3 days after MCAO, rat hippocampus damage was observed by Nissl's staining and TUNEL technique. In addition, water maze experiments were performanced 30 days after MCAO.Results Our results showed that behavior test scores were lower in MCAO+CBX group, compared with MCAO group. In the MCAO group, DND was 50% of the animals in hippocampal CA1 region after 3 days, which was 20% in the MCAO+CBX group. The DND positive rate of the MCAO+CBX group was significantly lower than that of MCAO group (p<0.05).30 days after ishchmia, rats of MCAO+CBX group showed a better performace in water maze task compare with those of MCAO group (p<0.05).Conclusion Blocking gap junction communication can reduce the incidence rate of DND in hippocampus after MCAO and improve the long-term cognitive function. All of the results sugget that gap junction communication plays a significant role in MCAO-induced remote hippocampal damage and cognitive impairment. Objective Here, we studied the effect of blocking gap junction communication after MCAO on the delayed neurnal death in ipsilateral hippocampus and further explored the mechanism.Materials and Methods Based on the genotypes of mice, they were divided into CX43+/+ sham group, CX43+/-sham group, CX43+/+ MCAO group and CX43+/-MCAO group. Behavior test was carried out 24h after MCAO. Then mice were killed at 3d after MCAO and the samples were harvested for further use. Neuronal cell popotosis in hippocampus were measured by TUNEL and water maze experiment was implemented at 30d after ischemia.Results Our results showed the behavior test scores of mice in CX43+/- MCAO group (2.36±0.21) were lower than CX43+/+ MCAO group (1.72±0.17). DND was detected in fewer mice in CX43+/- MCAO group than in CX43+/+ MCAO group. Mice of CX43+/- MCAO group performaced better in water maze task 30 days after MCAO than those of CX43+/+ MCAO group (p<0.05).Conclusion Blocking gap junction communication of glias may reduce incidence rate of delayed neuronal death in hippocampus after MCAO, which indicates that gap junction communication between glias plays an important role in MCAO-induced remote hippocampal damage and cognitive impairment. Part Two Spreading depression meditated by gap junctional communication contributes to hippocampal damage following MCAOA study on rat cortical and hippocampal spreading depression induced by MCAOObjective Spreading depression (SD) is a pathophysiological phenomenon observed in the CNS with characteristic ionic, metabolic and hemodynamic changes. SD plays an important role in some nervous system diseases, including migraine, cerebrovascular diseases, head injury and transient global amnesia. In the present study, we investigated the construction of the electrophysiological technique platform of SD in vivo. Furthermore, the recording method of SD was applied to the electrophysiological research of the region remote from ischemia area of focal cerebral ischemia.Methods The SD was elicited by MCAO cerebral ischemia. The Ag/AgCl electrode was applied to detect the SD by recorded the DC potential. Additionally, the method was improved and applied to electrophysiological research in the cortex and hippocampus of MCAO model.Results No SD wave was recorded before the MCAO cerebral ischemia model, while repeated huge negative DC potential shifts (SD waves) were recorded and during the 60 min following the ischemia. No visible DC potential change was recorded during the corresponding time course in the control group. Howerver, SD can be recorded in a part of MCAO rats during the 60min following the ischemia.Conclusion Here we established the electrophysiological technique platform of SD in vivo and we recorded SD waves in cortex and hippocampus following middle cerebral artery occlusion (MCAO) ischemia by this method. Research on the relationship between spreading depression and rat Hippocampus damage after MCAOObjective Hippocampal delayed neuronal death was observed after middle cerebral artery occlusion (MCAO). The mechanics of this remote damage has rarely been reported. Spreading depression (SD) is a pathophysiological phenomenon which plays an important role in various clinical disorders. The aim of this part is to explore the relationship between SD which was induced by focal cerebral ischemia and the DND in ipsilateral hippocampus after MCAO.Methods Rats were randomly divided into 3 groups, including sham group, MCAO group and MCAO+MK-801 group.30 min before MCAO, MK-801 (2 mg/kg body weight) was given to the rats in MCAO+MK801 group by intraperitoneal injection. A rat model of MCAO was made by the intraluminal suture technique. The SD waves were recorded by electrophysiological method with the technique platform constructed above. Delayed neuronal death in the hippocampus was observed by Nissl's staining and TUNEL labeling.Results In the SD inhibitor abesence group, DND was detected in 39% of the animals in hippocampal CA1 region 3 days after MCAO. Applying MK-801, the inhibitor of SD, DND only appeared in 10% of the animals in hippocampal CA1 region 3 days after MCAO.Conclusion Inhibition of SD significantly reduced the probability of hippocampal DND after MCAO. SD might have relation to DND in hippocampus after MCAO. Research on the effect of carbenoxolone on spreading depression elicited by MCAOObjective Prevous studies suggested that spreading depression plays an important role in nervensystem diseases. The mechanism of SD may be correlated to gap junction. The aim of this part is to explore the relationship between cortical and hippocampal SD elicited by focal cerebral ischemia and the gap junction blocker CBX.Methods Rats were randomly divided into 3 groups, sham group, MCAO group and MCAO+CBX group. CBX was injected into the lateral ventricle of the rats in MCAO+CBX group 2h before MCAO. A rat model of MCAO was made by the intraluminal suture technique. The SD waves were recorded by electrophysiological method with the technique platform constructed as above.Results The amplitudes of SD waves in the MCAO+CBX group were significantly reduced when compared to the MCAO group (p<0.05). Meanwhile, the positive rate of SD waves was also decreased significantly (p<0.05). However, the durations of SD waves was found no significant difference between the MCAO+CBX group and MCAO group (p>0.05).Conclusion Gap junction inhibitor CBX is effective to inhibit cortex and hippocampus SD induced by MCAO, suggesting the gap junction is involved in the development of SD.