Therapeutical Effects Of Intracerebroventricular Adminmistration Of P75 NTR-ED-Fc And The Underlying Mechanismsneural In PTSD Rats

Posttraumatic stress disorder(PTSD)is a permanent chronic psychological dysfunction involves the individual exposure to a life-threatening,death or catastrophic event.The main symptoms of PTSD include persistent and spontaneous recollection of the traumatic event,psychic numbing,increased arousal,avoidance of trauma associated stimuli and selective forgetting to wound experience.The patients of PTSD suffered psychological disorder and loss normal function which pose a huge burden on family life and society in a long period.However,it often co-morbidity with substance abuse,depression,anxiety,phobia,and.Thus,it is important to investigate the mechanism of PTSD and seek effective therapeutic target,for developing effective treatment and sustainable disease prevention.As a low-affinity neurotrophins receptor,p75 neurotrophin receptor(p75NTR)is a transmembrane receptor involved in a diverse array of cellular responses,including apoptosis,survival,neurite outgrowth,migration,and cell cycle arrest.Several lines of evidences indicate that p75 NTR involved in neuron survival and growth by promoting the brain-derived neurotrophic factor(BDNF)binding to tyrosine kinase B(Trk B)receptor with high affinity.What’s more,the p75 NTR involved in the inhibition of neurite growth as a co-receptor of Nogo-66 receptor(Ng R).Clinical data and animal experiments have shown that the reduction in hippocampus and volume of amygdala PTSD patients is closely related to neuronal apoptosis,while p75 NTR may plays a critical role in the process of apoptosis through caspase-9 and pro BDNF.Otherwise,it is easy to activate the traumatic memory in patients with PTSD and this fear-related memory can change the synaptic plasticity by adopting pro BDNF.Thus,p75 NTR may be involved in the pathophysiology of PTSD as a new therapeutic target.To explore the function of p75 NTR in hippocampal neuronal apoptosis and synaptic changes,this experience inhibits the activity of endogenous p75 NTR by injecting extracellular domain of p75NTR(p75NTR-ED-Fc)on rats with PTSD,and then,evaluate the therapeutic effect by behavior test and histology detection.The underlying molecular mechanism was helpful for providing a new reliable target of curing PTSD.Main research contents:1.Establish animal model and drug interventionsThe 8-week-old female SD rats were randomly divided into Control group,PTSD+p75NTR-ED-Fc group,PTSD+NS group and PTSD group,the model of PTSD was establish by single-prolonged stress(SPS).Then,PTSD + p75NTR-ED-Fc group was intervened by intracerebroventricular injection(ICV)p75NTR-ECD-Fc while the PTSD +NS group with normal saline.2.Behavior testIn order to estimate the treatment effect preliminarily,open-field test,elevated plus maze,Morris water maze was applied to the behavioral experiments.3.Study of histomorphology tectologyThe basic structure and morphology of hippocampus in rats were observed with H.E,NISSL and Golgi-cox staining.4.Study of the molecular mechanismsThe expression of cytokines and some receptors which may have influence in neuronal apoptosis,synaptic plasticity and neurite outgrowth,such as p75 NTR,Bcl-2,Caspase-3,rock-2,Synapsin I and p CREB was detected by immunofluorescence staining.Results and conclusions:1.Behavioral Date:(1)Resistant to capture test: Responses to the capture of PTSD group were significant higher than the results in Control group(P <0.01),while the resistant to capture score of PTSD + p75NTR-ED-Fc group wer lower than PTSD group(P<0.05).(2)Open field test: The rats in PTSD group showed significant difference in the grooming,freezing and rearing behaviors,Comparing to the Control group(P <0.01),and the time in central zone of PTSD + p75NTR-ED-Fc group was significantly highe when compare to the PTSD group(P <0.01).(3)Elevated plus maze: There were clear difference in the open arm entry and time spent in open arm between the PTSD + p75NTR-ED-Fc group and PTSD group.(4)Water maze test: No difference were found on the first escape latency of the 2nd,3rd and 6th day on the test,while the escape latency was prolong on the1 st,4th,5th day between the PTSD group and Control group(P <0.01).In water maze exploration test,there were differences on the times of target quadrant and crossingplatform in PTSD + p75NTR-ED-Fc group than in PTSD group.As a result,the injection of p75NTR-ED-Fc can be reduced the aggressive behavior and escape behavior,increasing their activity,relieve anxiety levels,and enhance learning and memory levels in a certain way.2.Study on the histomorphology tectology: In the control group,the cell bodies in the CA3 were well distributed and clearly structured,and the cells in the CA1 region was comparatively large and more cross sections of dendrite were evident in the stratum radiatum.In PTSD group,there are more cell debris in CA3 region and their structure is not clear.What’s more,the number of pyramidal cells in CA1 almost countable and sparse,only a small number of pyramidal cells was stained.In PTSD+p75NTR-ED-Fc group,cell density,there are no significant differences in shape and size between cells in CA3 aera.Pyramidal cells were evenly distributed with clearly visible branch with large angle in stratum radiatum of CA1 region.In addition,DG area shows a number of large moss cells which was significantly higher than PTSD group.3.Study on the molecular mechanisms: The DG area in hippocampus of PTSD group has a significant number of TUNEL-labeled cells(P<0.01)which was higher than the Control group,the expression of Bcl-2,Synapsin I and p CREB were lower than those in Control group,the expression of p75 NTR,Caspase-3 and ROCK-2 were lower than those in Control group.Compare to the PTSD group,the DG region in hippocampus of PTSD+p75NTR-ED-Fc group has a lower number of TUNEL-labeled cells(P<0.01)and the expression of Bcl-2,Synapsin I,p CREB was higher.Otherwise,the expression of p75 NTR,Caspase-3 and ROCK-2 were lower than those in PTSD group.That is to say,the improvement effect of behaviors in PTSD rats may result from the protective effects of hippocampal neurons and synaptic plasticity which caused by p75NTR-ED-Fc.