Effects Of Memantine On The Expression Of BDNF, NGF, ERK In Hippocampal Neurons Of Rats With Vascular

Background and ObjectiveVascular dementia (VaD) is a heterogeneous syndrome which has various clusters of symptom. Any dementia that is related to vascular factors can be called vascular dementia. In clinic, VaD is a kind of brain dysfunction resulted from various kinds of ischemic cerebrovascular diseases and characterized as.acquired intelligence damage and cognitive impairment syndrome. It is a chronic progressive disease, and its core symptom is cognitive impairment. Vascular dementia is the second common cause of dementia after following Alzheimer's disease (AD), and it accounts for 10%-50% of all dementias. With the increase of life expectancy and number of aging people, cerebrovascular diseases become more and more in number.As a result, the incidence of VaD is increasingly on the rise, which seriously affects the life quality of patients and also exerts a heavy financial and spirit burden on the families and the society. Therefore, studies on VaD attract widespread attention of many countrys around the world and they have considerably practical value for us.Memantine has been shown to have neuroprotective effects in vitro and in vivo studies. It was approved for moderate to severe AD by the European CPMP and the U.S. FDA respectively in 2002 and 2003. A systematic review and meta-analysis undertaken by Kavirajan suggests memantine has an effect on vascular dementia and it is well tolerated. The exact mechanism that memantine can improve cognitive function of patients with dementia is not fully clear. The current studies show that it is a medium affinity, non-competitive, voltage-dependent NMDA receptor antagonist.BDNF (Brain-derived neurotrophic factor), NGF (Nerve growth factor) are two important neurotrophic factors in the body. Some studies suggest that the expression of neurotrophic factors increases after cerebral ischemia, which can protect damaged brain cells and promote functional recovery of neurons. ERK is an important intracellular serine/threonine protein kinase, and its active form is p-ERK. Its substrates include other important intracellular kinases, transcription factors, histone, and K+ channel, etc. They are important components of cell and play an essential part in the process of learning and memory. ERK may be involved in the process of neuronal morphological plasticity.We establish rat model of vascular dementia and observe the learning and memory ability of rats, morphological changes of hippocampal neurons and expression of BDNF, NGF, and ERK in hippocampal neurons, which aims to explore the mechanism of memantine's treatment for vascular dementia and its neuroprotection.Materials and methods1 Animals and grouping 48 healthy male Wistar rats (from Henan Medical Center for experimental animals, age:14-15months, weight (400±50g) were randomly divided into sham-oprated group, VD group and memantine group (16 rats each group).2 Models and medication Rat models with vascular dementia were establisted by a permanent occlusion of bilateral common carotid arteries (2-VO). Then memantine 3mg/kg (dissolved in saline) was given to memantine group by intragastric administration once a day for 6 weeks. Sham-oprated group and VD group were given the same dose saline once a day for 6 weeks.3 Test of learning and memory The learning ability was oberserved by Y-maze test after the oral administration. The rats with 9 correct responses in 10 tests could meet the criteria set by us. We recorded the number of electric shock when the rats reached the standard. The number of electric shock was regarded as the representive of learning ability. The experimental process mentioned above was repeated to observe the rats' memory ability.4 Specimens The rats were killed to make histological section after the learning and memory test. The changes of cell morphology and expression of BDNF, NGF and ERK in hippocampal neurons were observed by HE staining and immunohistochemistry technique respectively.5 Assessment of immunohistochemistry result The positive cells of BDNF, NGF and ERK were stained brown in cytoplasm. The expression of BDNF, NGF and ERK were measured by Qwin550CW image processing and analysis system.6 Statistical anylysis All data were dealed with SPSS 13.0 statistic software. All the data were expressed with (x±s).They were analyzed among groups using One-Way analysis of variance and compared between two groups using S-N-K method. The testing standard was a=0.05.Results1 Learning and memory performance Compared with VD group and sham-operated group, the learning and memory performance in the memantine group were between the former two groups (learning performance:61.94±3.62,79.63±4.18, 47.69±3.05, F=308.146, P<0.05; memory performance:49.94±3.96,69.81±3.94, 38.44±2.66, F=316.405, P<0.05):The performances in the three groups were significantly different.2 The HE staining The sham-operated group showed that the neurons arrangement was uniform and tidy, the nuclei were large and round and nucleoli were clear. The VD group demonstrated that neurons arranged loosely, their structures were unclear, and nuclears were shrinking. The memantine group showed that neurons arranged tightly, the nulei were round, nucleoluses were clear and a few shrinking and dagenerative neurons were observed.3 The results of immunohistochemistry BDNF, NGFand ERK positive cells were stained brown in cytoplasm. Only few moderate-stained BDNF, NGF positive cells were observed in sham-operated group. A large number of deep-stained BDNF, NGF positive cells were observed in VD group. The number of BDNF, NGF positive cells in memantine group was more than that in sham-operated group and VD group. Many ERK positive neurons were expressed in hippocampus CA1 area and endochylema is colorized deeply brown in sham-operated group. A few ERK positive neurons were observed and the layers of structure were loose in VD group. A lot of ERK positive neurons were observed and the layers of structure were clear and close in memantine group. The average gray value in BDNF positive area:109.94±4.82, 137.78±6.46,174.12±6.90, F=510.439, P<0.05; the average gray value in NGF positive area:106.17±5.53,130.65±5.07,165.95±6.14, F=461.602, P<0.05; The average gray value in ERK positive area:164.05±6.62,99.50±7.28,131.24±7.32, F=332.431, P<0.05.Conclusion1. Memantine can alleviate hippocampal neuronal ischemic necrosis of rats with vascular dementia, have neuroprotective effects and improve rats' learning and memory ability.2. The increase of expression of BDNF, NGF and decrease of expression of ERK in hippocampal neurons are involved in the development of vascular dementia.3. Memantine plays a neuroprotective role by increasing the endogenous expression of BDNF and NGF. It can also improve learning and memory of rats with vascular dementia by increasing the expression of ERK.