Effect Of Dexmedetomidine Hydrochloride On Inflammatory Responses Of Hippocampal Neurons After Subarachnoid Hemorrhage In Rats

Research Objective: Subarachnoid hemorrhage(SAH)is the most common phenomenon in neurosurgery,which is caused by intracranial aneurysm rupture,and has high morbidity and mortality.In recent years,experts and scholars put forward early brain injury(early brain injury,EBI)this concept,in the acute injury of window period is accompanied by a series of complicated pathophysiologic changes,such as increased intracranial pressure,inflammation,reduced cerebral blood flow,blood brain barrier damage and brain edema,and so on.In a recent clinical trial has reported that inflammation play an important role in the EBI,seriously affecting the prognosis of patients.In basic research,it was found that SAH had the most serious effect on hippocampal neurons.Dexmedetomidine(Dex)is a highly selective alpha 2 adrenergic receptor agonist with sedative,analgesic,antisympathetic,anti-anxiety and anti-inflammatory effects.It has become a commonly used drug in clinical anesthesia.At present,the anti-inflammatory effect of Dex has become the focus of research.It has been reported that Dex has a protective effect on hippocampal neurons.This study aim to explore two issues: 1.To investigate the changes of inflammatory mediators in hippocampal neurons of rats with EBI after SAH and whether it changes with different time points.2.To investigate the effect of Dex on inflammatory mediators and downstream proteins in rats with EBI after SAH.Research methods: Part I: The classic method of second blood injection into the cisterna magna was used to establish the animal model of subarachnoid hemorrhage in rats.At the time points of 6h,12 h,24h,36 h and 72 h after surgery,the animal model was evaluated by neurological function score,SAH score and brain water content measurement.The expression differences of NLRP3,IL-1? and IL-18 proteins in the hippocampus of rats after SAH were detected by Western blot.Part II: Dexmedetomidine(25ug/kg)was intraperitoneally injected 2 hours after the model was established by second blood injection.Using neurological function score,SAH score and brain water content measurement to evaluate the dexmedetomidine the effects on rat hippocampus,using Western blot method to detect NLRP3 in rat hippocampus after subarachnoid hemorrhage,IL – 1?,IL-18 protein expression changes,with hematoxylin-eosin staining method(HE staining),observe the change of rat hippocampal neurons form,using immunohistochemical method to detect after subarachnoid hemorrhage rat hippocampal neurons in the distribution changes of NLRP3 protein.Results: Part I: Neurological function score test results showed that the neurological function of SAH group was significantly reduced compared with the sham operation group,and the intra-group comparison was most significant at 12 h.The experimental results of SAH score and brain water content showed that SAH score and brain water content were significantly increased in the SAH group and the sham operation group,and the increase was most significant at the time point of 12 h.Western blot results showed that NLRP3,IL-1?,and IL-18 related proteins increased at different time points in hippocampal neurons in SAH group and sham operation group,and the increase was most significant at 12 h in the group.Part II: Neurological function score showed no statistical difference between SAH+Dex group and Sham+Saline group;neurological function of rats was improved by comparison between SAH+Dex group and SAH+Saline group.SAH scoring results showed that there was a statistical difference between the SAH+Dex group and the Sham+Saline group,while no statistical difference was found between the SAH+Dex group and the SAH+Saline group.Brain water content showed that there was no statistical difference between the SAH+Dex group and the Sham+Saline group,and the difference between the SAH+Dex group and the SAH+Saline group was significant.Western blot results showed that compared with Sham+Saline group,the expressions of NLRP3,IL-1? and IL-18 protein were not statistically significant.Compared with SAH+Saline group,the expressions of NLRP3,IL-1? and IL-18 protein in rat hippocampus were significantly decreased.HE staining showed that no statistical difference was found between the SAH+Dex group and Sham+Saline group.The comparison between the SAH+Dex group and SAH+Saline group could significantly improve the cell arrangement in the DG area of the hippocampus of rats and reduce the edema of the hippocampal nerve cells of rats.Immunohistochemistry results showed that there was no significant difference in the number of immunologically positive cells of NLRP3 between the SAH+Dex group and the Sham+Saline group,while there was a significant difference in the number of immunologically positive cells of NLRP3 between the SAH+Dex group and the SAH+Saline group,and the difference was statistically significant.Conclusion: In the early brain injury after subarachnoid hemorrhage in rats,there was neurological damage,cerebral edema,and expression of inflammatory factors in hippocampal neurons,and it was the most severe at 12 h after hemorrhage,which was relieved with time.However,there is still damage compared with the sham group.Dexmedetomidine can improve the damage of hippocampal neurons in early brain injury after SAH,reduce brain edema,and reduce the expression of inflammasome in hippocampal neurons.