| Objective:To study the protective mechanism of Dendrobium on hippocampus in rats with cognitive dysfunction induced by STZ(streptozotocin,STZ),and to provide a new idea for further study on prevention and treatment of Alzheimer's disease.Methods:There are 40 male Wistar rats,weighting about 220g and belonging to SPF grade,which were randomly divided into five groups after being fed for a week.Among them,there are 8 rats in the normal group,and the rest 32 were dealt with intracerebroventricular injection(ICV).For the normal group,the rats were fed regularly,and for the 8 rats in sham operation group,they were injected with 10 ?L normal saline instead of streptozotocin.The others were injected with intracerebroventricular with 10%streptozotocin for the first and the third day.A week later,experiment of Morris water maze was done to observe the behavior of rats,and then randomly divided them into following three groups according to the experimental results:model group,low-dosage group and high-dosage group.After four weeks,treated by dendnobium compound,experiment of Morris water maze was repeated to observe their behavior.After 10 hours' fasting,the sampling four rats from each group were anesthetized with 1000mg/kg urethane(10%concentration is commonly used).The four rats were dealt with systemic perfusion until the liver and limbs become stiff,firstly using normal saline and then 4%paraformaldehyde solution.We decapitated the rats and take the brain and hippocampus out,and then perform HE staining and Congo red staining on hippocampus tissue.The severity of photoreceptor apoptosis of nerve cells in hippocampus tissue was tested by TUNEL method.As for the rest,we get the hippocampus tissue,and the expression of protein and mRNA for Bcl-2,Bax and Caspase-3 were checked using KT-Qpcr and Western bolt.Results:1.General observation on rats:Rats in normal group were in good condition for eating and drinking.The rats in the sham operation group did badly in mobility,but normally in eating and drinking.The rats in the experimental group were exposed to hairiness,and the mobility was weakened and the weight was reduced.After the treatment,the situation was improved.2.Morris water maze experiment on rats:Before the intervention,in comparision with the normal group,rats in the the sham operation group and the model group spent more time in searching the underwater platform and the times of crossing platform was significantly different(P<0.01).After the intervention of the drug,for the rats in high-dosage group,the time of getting to the underwater platform was longer and times of crossing platform increased.But it was not statistically different from the model group(P=0.067).The time in searching the underwater platform and the times of crossing platform between the sham operation group and the model group rats was significantly different(P<0.01).When it comes to the rats in sham operation group and the normal group,it is significantly different,too(P<0.01).3.HE staining on hippocampus of rats:There are plenty of cells in normal group with normal structure,which are set in order,distributed evenly,stained normally.The number of cells in the model group was decreased,and the volume of cells was reduced.The cells were irregularly arranged,whose distribution was uneven.The nucleus was fixed and the staining was deepened.After intervention,comparing with the model group,the number of cells in the high-dosage group and low-dosage group increased,and the intracellular structure and the arrangement were improved,and the staining was normal,too.4.Congo red staining on hippocampus of rats:The number of orange cells in the model group was significantly higher than that in the normal group(P<0.01).After the intervention,comparing with the model group,the numbers of orange cells in the high-dosage and the low-dosage group were reduced and significantly different(P<0.01).Compared with the high-dosage group,the orange cells in the low-dosage group were decreased statistically.(P<0.05).5.TUNEL based apoptosis detection on hippocampus of rats:Comparing with the normal group,the number of orange cells in the model group increased and it had significant difference(P<0.01).After the intervention,comparing with the model group,t the orange cells in the low-dosage group decreased with a statistically significant difference(P<0.01).6.The expression of Bax,Bcl-2 and Caspase-3 mRNA on hippocampus of rats:Comparing with the rats in normal group,the expression of Bcl-2mRNA in model group decreased with a statistically significant difference(P<0.05),and the expression of Bax and Caspase-3 was significantly increased(P<0.01).After the intervention,comparing with the model group,the expression of Bcl-2mRNA in the low-dosage group increased but without significant difference(P= 0.0503),and the expression of BaxmRNA and Caspase-3Mrna decreased significantly(P<0.01).The expression of Caspase-3mRNA in the high-dosage group decreased but without significant difference(P>0.05),and the expression of Bcl-2mRNA increased without significant difference(P>0.05).Meanwhile,the expression of BaxmRNA decreased with a statistically significant difference(P<0.01).7.The expression of Bax,Bcl-2 and Caspase-3 on hippocampus of rats:Comparing with the normal group,the expression of Bcl-2 in the model group decreased with a statistically significant difference(P<0.05),and the expression of Bax and Caspase-3 significantly increased(P<0.01).After the intervention of drug,comparing with the model group,the expression of Bcl-2 in the high-dosage group and low-dosage group increased significantly(P<0.05),and the expression of Bax decreased with a statistically significant difference(P<0.05),and the expression of Caspase-3 decreased significantly(P<0.01).Conclusion:1.Dendrobium mixture can improve the learning and memory ability of the rats with cognitive dysfunction induced by STZ;2.Dendrobium mixture can improve the tissue plaque deposition and the degree of apoptosis and necrosis of rats with cognitive dysfunction induced by STZ;3.Dendrobium may supress the brain damage of rats with cognitive dysfunction by up-regulating Bcl-2 and down-regulating the expression of Bax and Caspase-3. |
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