Microwave Exposure Impairs Synaptic Plasticity in the Rat Hippocampus and PC12 Cells through Over-activation of the NMDA Receptor Signaling Pathway

Objective The aim of this study is to investigate whether microwave exposure would affect the N-methyI-D-aspartate receptor （NMDAR） signaling pathway to establish whether this plays a role in synaptic plasticity impairment. Methods 48 male Wistar rats were exposed to 30 mW/cm^2 microwave for 10 min every other day for three times. Hippocampal structure was observed through H＆E staining and transmission electron microscope. PC12 cells were exposed to 30 mW/cm^2 microwave for 5 min and the synapse morphology was visualized with scanning electron microscope and atomic force microscope. The release of amino acid neurotransmitters and calcium influx were detected. The expressions of several key NMDAR signaling molecules were evaluated. Results Microwave exposure caused injury in rat hippocampal structure and PC12 cells, especially the structure and quantity of synapses. The ratio of glutamic acid and gamma-aminobutyric acid neurotransmitters was increased and the intracellular calcium level was elevated in PC12 cells. A significant change in NMDAR subunits （NR1, NR2A, and NR2B） and related signaling molecules （CaZ＋/calmodulin-dependent kinase II gamma and phosphorylated cAMP-response element binding protein） were examined. Conclusion 30 mW/cm^2 microwave exposure resulted in alterations of synaptic structure, amino acid neurotransmitter release and calcium influx. NMDAR signaling molecules were closely associated with impaired synaptic plasticity.

Developmental Lead Exposure Alters the Distribution of Protein Kinase C Activity in the Rat Hippocampus

Chronic low-level lead (Pb) exposure in children is known to cause a deficit in learning and memory. In vitro studies have demonstrated that Pb altered protein kinase C (PKC) activityt Especially, hippocampal PKC has been correlated with performance in several learning tasks. The effects of Pb exposure on hippocampal PKC were investigated during development at various postnatal ages: postnatal day (PN) 7, 14, 28, and 56. Two-tenth % Pb acetate was administered to pregnant and lactating dams and then administered to weanling rats in drinking water. PKC activity was measured in both membrane and cytosolic fractions from the hippocampi of the controls and Pb-exposed animals. Pb-induced increase in PKC activity in the cytosolic fraction was obsereved in the PN56 rats. In contrast, PKC activity was decreased by Pb at PN7 in the membrane fraction. Furthermore, a significant decrease in the ratio of membrane to cytosolic PKC activity which is representative of PKC distribution was observed in the PN28 and PN56 Pb-exposed rats relative to the same-age controls. This study indicates that chronic Pb exposure during development influences hippocampal PKC activity and distribution. These changes may be involved in the subclinical neurotoxicity of chronic Pb exposure in young children.

Expression of prostaglandin E_2 receptors in rat hippocampus

BACKGROUND: Prostaglandin E2 (PGE2) can directly regulate toxic injury of hippocampal neurons through participation by its receptor. Increase of excitability of hippocampal membrane and long-term synaptic elasticity are closely related to PGE2, PGD2 and PGF2A. This suggests that PGE2 may be a key molecule of neuronal signal passage and regulate the existence of neurons through its receptor. However, which isoforms of PGE2 receptor expressing in hippocampal neurons is still unclear. OBJECTIVE: To research the subtype expression of PGE2 receptor in hippocampus of rats through mRNA transcription and protein interpretation. DESIGN: Animal studies with random, control and operator and designer double-blind methods. SETTING: University of South Carolina, Animal Center. MATERIALS: Sprague-Dawley rats, aged 12 weeks, weighing 200 g, females 48 and males 48, were selected from Animal Center in South Carolina University. Tri ReagentTM kit was provided by Molecular Research Center, USA. METHODS: The experiment was carried out in Animal Center in South Carolina University from January to December 2005. The expression of the PGE2 receptors was profiled and compared in rat hippocampus using real-time RT-PCR and Western-blot techniques. MAIN OUTCOME MEASURES: Expression of PGE2 receptors in various isoforms of hippocampal neurons of rats. RESULTS: mRNAs of all four EP1-4 subtypes were detected in the hippocampus. Western-blot data showed consistently detectable bands at approximately Mr 50 000 of EP1, Mr 40 000 and Mr 52 000 of EP2, Mr 45 000, Mr 57 000 and Mr 105 000 of EP3, and Mr 46 000 of EP4. CONCLUSION: Identifying four subtypes of EPs heterogeneously expresses in the hippocampus.

EFFECTS OF GINSENOSIDE Rb1 AND Rg1 ON SYNAPTOSOMAL FREE CALCIUM LEVEL, ATPase AND CALMODULIN IN RAT HIPPOCAMPUS

Calcium homeostasis in synaptosomes is altered during aging. The intrasynaptomal free calcium concentration ([Ca2+]i) was determined in 3- and 24-month-old rats treated with or without Rbl and Rgl. As expected, the [Ca2-]i level increased with age. Treatment with Rbl and Rgl elicited an obvious decrease of [Ca2+]i content, especially in aged rates. In addition, Rbl and Rgl significantly stimulated the activity of Na+, K+-ATPase while Rbl inhibited the activity of Ca2+, Mg2--ATPase arid calmodulin. In view of the close relationship of [Ca2-]i level with aging, the changes of [Ca2+]i induced by Rbl and Rgl, as shown by our results, might provide an explanation of the mechanisms of their antiaging function.

Inhibition of the Specific ~3H-DL-Glu Binding in the Hippocampus of Rat Brain by Lead

The effect of Pb2+ on 3H-DL-Glutamate (3H-DL-Glu) binding in the membrane preparations from the hippocampus of rat brain was investigated with a view to explaining the cognitive and learning deficits produced by the heavy metal. The results indicated that Pb2+ (3. 1-25. 0 μmol.L -1 ) inhibited 3 H-DL-Glu binding in a concentration-dependent manner . Scatchard analysis further revealed that at a concentration of 6. 3 μmol.L-1 Pb2 + interfered with binding mainly through significantly decreasing the density of binding sites. This finding provided an important insight into Pb2+ -induced impairments in learning and memory previously documented in children and in experimental animals chronically exposed to Pb^(2+)

Effect of different therapies of Chinese medicine on the expressions of c-Fos and c-Jun proteins in hippocampus of rats with post-stroke depression

BACKGROUND ： c-fos and c-jun, the important immediate early genes （IEG）, are regarded as the markers for the location and function of neuronal activity, as well as the third signal messengers, they couple the stress stimulation and the gene expression in neuron, and hippocampus is involved in the process of signal transmission after stress stimulation induced depression. OBJECTIVE： To observe the therapeutic effects of Bushen Yiqi （tonifying kidney to benefit qi）, Huoxue Huayu （promoting blood circulation to dissipate blood stasis） and Ditan Kaiqiao （eliminating phlegm for resuscitation） on the expressions of c-Fos and c-Jun proteins in hippocampus and spontaneous behaviors of rats with post-stroke depression （PSD）, and compare the results with those of fluoxetine, which is known to have definite effect on depression. DESIGN： A randomized controlled tna SETTING ： Zhejiang College of Traditional Chinese Medicine MATERIALS ： The trial was completed in Zhejiang College of Traditional Chinese Medicine from January to July in 2003. Fifty-six healthy adult Wistar male rats of clean grade, weighing （250±50） g, were randomly divided into 7 groups with 8 rats in each group： control group, model group, forced swimming group, Bushen Yiqi group; Huoxue Huayu, Ditan Kaiqiao group and fluoxetine group. The Bushen Yiqi Tang contained Renshen, Huangqi, Heshouwu, Gouqi, Shudi, etc., crude drugs 1 800 g/L. The Huoxue Huayu Tang contained Danshen, Chuanxiong, Chishao, Yujin, etc., crude drugs 3 600 g/L. The Ditan Kaiqiao Tang contained Banxia, Danxing, Changpu, Yuanzhi, etc., crude drug 1 000 g/b METHODS： ① Except the control group and forced swimming group, rats in the other groups were made into PSD models by deligating the bilateral common carotid artedes permanently. ② Rats in the control group, model group and forced swimming group were intragastncally perfused by saline （3 mL for each time）; those in the Bushen Yiqi group, Huoxue Huayu, Ditan Kaiqiao group and fluoxetine group were intragastncally perfused with Bushen Yiqi Tang （18 g/kg）, Huoxue Huayu Tang （9 g/kg）, Ditan Kaiqiao Tang （9 g/kg） and fluoxetine （2.5 mg/kg） respectively, once a day. ③ At 55 days after model establishment, rats in the forced swimming group were managed according to the Porsolt＇s method. They were placed in water for 15 minutes, and then taken out and dned, no moving-time within 5 minutes was recorded at drying and 24 hours after drying. ④ Measurement of spontaneous behaviors： Except the forced swimming group, the spontaneous behaviors and activities （including horizontal and vertical movements） of rats were observed with the Open-Field method at 28, 42 and 56 days after administration in the other groups. ⑤ The expressions of c-Fos and coJun proteins in hippocampus were determined with the immunohistochemical method, the relative sectional area ratio and average objective gray value of c-Fos and c-Jun positive cells in hip- pocampus were measured with the computerized image analytical system. MAIN OUTCOME MEASURES： The spontaneous behaviors of rats, the relative sectional area ratio and average objective gray value of c-Fos and c-Jun positive cells in hippocampus were observed. RESULTS： Of the 56 rats, 1 died in the forced swimming group, and finally 55 rats were involved in the analysis of results. ① Results of spontaneous activities： At 28 days, the times of crossing movements were obviously fewer in the model group and fluoxetine group [（69.00±37.01）, （98.11 ±36.68） times/3 minutes] than in the control group [（128.44±16.85） times/3 minutes, P 〈 0.01, 0.05], but those in the Bushen Yiqi group, Huoxue Quyu group and Ditan Kaiqiao group had no obvious differences as compared with those in the control group （P 〉 0.05）. At 42 and 56 days, the times of crossing movements were obviously more in the Bushen Yiqi group, Huoxue Quyu group and Ditan Kaiqiao group [（106.44±31.24）, （117.20±23.95）, （134.80±28.18）, （136.36±40.95） times/3 minutes; （117.33±35.91）, （129.60 ±23.78）, （131.90 ±26.81）, （136.09±28.34） times/3 minutes] than in the model group [（64.00±17.51）, （72.86±20.68） times/3 minutes, P 〈 0.01]. The times of rearing movements had no obvious differences among the groups for the three times （P 〉 0.05）. ② The no moving-time within 5 minutes 24 hours after drying was obviously longer than that at drying in the forced swimming group. ③ The average objective gray values of c-Fos positive cells were not obviously different in the Bushen Yiqi group and Ditan Kaiqiao group from the control group （P 〉 0.05）, but lower in the model group than in the control group （69.84±9.82, 75.78±5.89, P 〈 0.01）, and higher in the forced swimming group than in the control group （85.97±10.99, P 〈 0.01）; all higher in the fluoxetine group, Bushen Yiqi group, Huoxue Quyu group and Ditan Kaiqiao group than in the model group （81.27±10.73, 74.04±8.34, 83.29±9.89, 70.14±4.92, P 〈 0.05-0.01）. The average objective gray values of c-Jun positive cells were obviously lower in the Bushen Yiqi group than in the control group （68.11 ±6.89, 79.58±5.86, P 〈 0.01）, but all higher in the other groups than in the control group （84.68±7.15, 81.34 ±8.36, 97.51±10.55, 85.68±9.25, 86.19±10.98, P 〈 0.05-0.01）; Those were obviously higher in the fluoxetine group, Huoxue Quyu group and Ditan Kaiqiao group than in the model group （P 〈 0.05-0.01 ）, lower in the Bushen Yiqi group than in the model group （P 〈 0.05）, all obviously lower in the Bushen Yiqi group, Huoxue Quyu group and Ditan Kaiqiao group than in the fluoxetine group （P 〈 0.01）. The relative sectional area ratios of c-Fos and c-Jun positive cells had no obvious differences among the groups （P 〉 0.05）. CONCLUSION ： The methods of Bushen Yiqi, Huoxue Quyu and Ditan Kaiqiao can effectively treat PSD in rats, and the results were equivalent with those of fluoxetine, the actions of the above-mentioned drugs may correlated with their regulation to c-Fos and c-Jun expressions in hippocampus. PSD animal models can be successfully established by both permanent deligation of bilateral common carotid arteries and forced swimming, and the models induced by the former has similar basic cerebrovascular lesions as human stroke in clinic.

Features of animal models of complex partial epilepsy established through unilateral,bilateral and alternate-side kindling at hippocampus of rats

BACKGROUND： Electrical stimulation kindling model, having epilepsy-inducing and spontaneous seizure and other advantages, is a very ideal experimental animal model. But the kindling effect might be different at different sites. OBJECTIVE： To compare the features of animal models of complex partial epilepsy established through unilateral, bilateral and alternate-side kindling at hippocampus and successful rate of modeling among these 3 different ways. DESIGN： A randomized and controlled animal experiment SETTING： Department of Neurology, Qilu Hospital, Shandong University MATERIALS： Totally 60 healthy adult Wistar rats, weighing 200 to 300 g, of either gender, were used in this experiment. BL-410 biological functional experimental system （Taimeng Science and Technology Co. Ltd, Chengdu） and SE-7102 type electronic stimulator （Guangdian Company, Japan） were used in the experiment. METHODS： This experiment was carried out in the Experimental Animal Center of Shandong University from April to June 2004. After rats were anesthetized, electrode was implanted into the hippocampus. From the first day of measurement of afterdischarge threshold value, rats were given two-square-wave suprathreshold stimulation once per day with 400 μA intensity, 1ms wave length, 60 Hz frequency for 1 s duration. Left hippocampus was stimulated in unilateral kindling group, bilateral hippocampi were stimulated in bilateral kindling group, and left and right hippocampi were stimulated alternately every day in the alternate-side kindling group. Seizure intensity was scored： grade 0： normal, 1： wet dog-like shivering, facial spasm, such as, winking, touching the beard, rhythmic chewing and so on; 2： rhythmic nodding; 3： forelimb spasm;4： standing accompanied by bilateral forelimb spasm;5： tumbling, losing balance, four limbs spasm. Modeling was successful when seizure intensity reached grade 5. t test was used for the comparison of mean value between two samples. MAIN OUTCOME MEASURES： Comparison of the successful rate of modeling, the times of stimulation to reach intensity of grade 5, the lasting time of seizure of grade 3 of rats in each group. RESULTS： Four rats of alternate-side kindling group dropped out due to infection-induced electrode loss, and 56 rats were involved in the result analysis. The successful rate of unilateral kindling group, bilateral kin- dling group and alternate-side kindling group was 55%（11/20）,100%（16/16）and 100%（20/20）, respective- ly. The stimuli to reach the grade 5 spasm were significantly more in the bilateral kindling group than in the unilateral kindling group [（30.63±3.48）, （19.36±3.47）times, t=8.268, P 〈 0.01], and those were significantly fewer in the alternate-side kindling group than in the unilateral kindling group [（ 10.85±1.98）times, t=-8.744, P 〈 0.01]. The duration of grade 3 spasm was significantly longer in the bilateral kindling group than in the unilateral kindling group [（9.75±2.59）, （3.21 ±1.58）days,t=-8.183,P 〈 0.01], Among 20 successful rats of al- ternate-side kindling group, grade 5 spasm was found in the left hippocampi of 11 rats, but grade 3 spasm in their right hippocampi; Grade 5 spasm was found in the right hippocampi of the other 9 rats, grade 4 spasm in the left hippocampus of 1 rat and grade 3 of 8 rats. CONCLUSION ： The speed of establishing epilepsy seizure model by alternate-side kindling is faster than that by unilateral kindling, while that by bilateral kindling is slower than that by unilateral kindling. The successful rate is very high to establish complex partial epilepsy with alternate-side or bilateral kindling. Epilepsy seizure established by alternate-side kindling has antagonistic effect of kindling and the seizure duration of grade 3 spasm is prolonged.

Sexual differences of the effects of prenatal stress on the expression of extracellular signal-regulated kinaseas in the hippocampus of offspring rats

BACKGROUND： Prenatal stress has been shown to inhibit cell proliferation in the dentate gyrus and hippocampus, reduce hippocampal volume, and cause neuronal loss and oxidative damage in the hippocampus of offspring rats, but the sexual difference of the effects on offsprings is seldom referred to. OBJECTIVE： To observe the effect of prenatal stress to adult pregnant rats on expression of extracellular signal-regulated kinases （ERK） in hippocampus of the offspring rats of different genders. DESIGN ： A randomized and control animal experiment.SETTING： Department of Physiology and Pathophysiology, School of Medicine, Xi＇an Jiaotong University. MATERIALS ： The experiments were carried out in the Key Laboratory of Environment and Gene Related Diseases （Xi＇an Jiaotong University）, Ministry of Education between October 2005 and March 2006. Fifteen female and five male adult Sprague-Dawley rats were adopted. Female rats weighing 230-250 g and male rats weighing 280-350 g were used. METHODS： The virgin female rats were placed overnight with adult male rats （3：1） for mating. A total of twelve pregnant rats were randomly assigned to prenatal stress group （PNS group, n=6） and control group （n=6）. The pregnant rats of the PNS group were exposed to restraint stress on days 14-20 of pregnancy three times a day, 45 minutes for each time . The restraint device was a transparent plastic tube （6.8 cm in diameter） with air holes for breathing and closed end. The length could be adjusted to accommodate the size of the animals. To prevent habituation of animals to the daily procedure, restraint periods were randomly shifted within certain time periods （8：00-11：00, 11：00-14：00, and 16：00-19：00）. After birth, offsprings of all groups were culled to 8-10 litters in each group and housed in the same animal room, and kept together with their biologic mothers. The pregnant rats of the control group were left undisturbed. On day 21, after all the offspring were weaned, male and female pups were separated and housed four in each cage respectively until test at 30 days of age. At the end of postnatal day 30, one male and female offspring rats from the same dam were selected with a random choice and a total of 24 animals from 12 different dams were used. The experimental rats were sacrificed by decapitation under anesthesia. Bilateral hippocampal tissues were isolated and homogenized in cold condition. Alkaline carbonate buffer （BCA） method was used to detect the concentration of extracellular signal-regulated kinases （ERK）, then mixed with loading buffer, the constant voltage was 100 V. Finally, BCIP/NBT staining and electrDphoresis were performed, the absorbance （A） value for the bands was detected with the Bandscan analytical software, and the expression of ERK in hippocampus of offspring rats of different genders in each group was quantitatively analyzed. MAIN OUTCOME MEASURES： The level of ERK expression in hippocampus of offspring rats of different genders in each group was observed.RESULTS： All the 24 offspring rats were involved in the analysis of results. ① The staining results of ERP activity in the extract of brain tissue detected with Western blotting technique and specific antibody analysis showed that the ERP in hippocampus of offspring rats had two subtypes of ERK-1 and ERK-2, and the latter was the main type.② Standardized by the average A value in the control group, the quantitative data of the general A value of total ERK showed that the expression of ERK-2 in hippocampus of female offspring rats was obviously higher in the PNS group than in the control group （A value： 126±6.76,100±4.89,P〈 0.01）. ③The expression of ERK-2 had no obvious difference between the female and male offspring rats in the control group.④ The expression of ERK-2 in hippocampus of male offspring rats was a little higher in the PNS group than in the control group （A value： 104±6.27,102±5.48,P 〉 0.05）. CONCLUSION ： PNS significantly affects the increase of ERK expression in hippocampus of female offspring rats, but has no obvious influence on that of male ones.

Effect of electroacupuncture on synaptic transmission in dentate gyrus of the hippocampus in cerebral ischemic injured rats

BACKGROUND： Some studies suggest that the long-term potentiation （LTP） of synaptic transmission may be the basis for the neural synaptic plasticity of hippocampus, but can be evoked by various factors including electroacupuncture. OBJECTIVE： To observe the effect of electroacupuncture on the activities of basic synaptic transmission in dentate gyrus of hippocampus and the changes of high frequency stimulation （HFS） induced activity of synaptic transmission in cerebral ischemic injured rats. DESIGN： A randomized control trial.SETTING： Shenzhen Hospital of Traditional Chinese Medicine affiliated to Guangzhou University of Traditional Chinese Medicine. MATERIALS： Sixty healthy male Wistar rats, weighing 150-250 g, were provided by the Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine. The experiment began after adaptation of environment for 1 week under standard experimental environment. The main experimental instruments included the programming electrical acupuncture apparatus （PCEA, product of the Institute of Acupuncture and Meridians, Anhui College of Traditional Chinese Medicine） and multichannel physiologic recorder （RM-86, Nihon Konden）. METHODS： The experiment was carried out in Guangzhou University of Traditional Chinese Medicine between July 2003 and July 2004. ①Embedding of brain electrodes： In reference of the Pellegrino＇s rat brain atlas, the bipolar electrode stimulator was embedded into the perforant path （PP） anterior to the entorhinal area with location coordinates of AP 7.5 mm, L 4.2 mm and H 3.0 mm, that is, 7.5 mm posterior to the anterior fontanelle, 4.2 mm laterally on the right side and 3.0 mm under the subcortex. The subcortex recorder electrode coordinates are AP 3.8 mm, L 2.5 mm and H 3.5 mm, located in the granular cell layer of the unilateral dentate gyrus （DG） of hippocampus, at the site of which an opening with the diameter of 1.5 mm was drilled for the purpose of embedding of the stimulating and recording electrodes, and at the site by mild adjusting the positions of these electrodes where maximal population spike （PS） was recorded, fastened the electrodes at last. ② The 60 rats were randomized into two major groups, namely, fundamental stimulation （FS） group （basic group） and high frequency stimulation （HFS） group. Each group was further divided into three subgroups respectively： Sham-operated subgroup （n=10）： only exposed bilateral common carotid arteries without blocking their blood flow; Cerebral ischemia model subgroup （n=10）： exposing bilateral common carotid arteries and blocking their blood flow; Ischemia plus electroacupuncture subgroup （n=10）： blocked blood flow of bilateral common carotid arteries and received electroacupuncture. The electroacupuncture acupoints were the points of Du meridian, including Baihui （GV20）, Dazhui （GV14）, and points of Pen meridian, including Qihai （CV6） and Guanyuan （CV4）. ③ Process of electroacupuncture： All the rats underwent testing stimulation （1/30 Hz frequency and 0.1 ms breadth） at 30 minutes before modeling, PS values were recorded as the indexes of the excitation of DG granular cell population, and the data were input to computer for data analysis. During the experiment, the intensity of stimulation was kept stable by adopting 1/2 the value of stimulation intensity that could induce maximal PS amplitude. In the basic group, PS were recorded for 120 minutes after modeling, and among the rats in the electroacupuncture group, PS was recorded at 10 minutes before and 60 minutes after blocking blood flow in the carotid artery during continuous electrical acupuncture. In the HFS group, HFS was given immediately after modeling, PS were recorded for 180 minutes at 10 minutes after HFS was given in the sham-operated group and model group, rats in the electroacupuncture group were treated with electroacupuncture for 60 minutes at 30 minutes after HFS was given, and PS was recorded for 180 minutes after 10 minutes. LTP was triggered by HFS and PS values were determined and recorded through measuring stimulations respectively 0, 10, 30, 60, 120 and 180 minutes after the evokes.④ Methods for expressing the level of synaptic transmission： Each testing stimulus provoked one PS, and 10 successive amplitude values （V/mV） were averaged relevant to a certain time cut. The averaged PS of 6 time cuts at 30 minutes before modeling was made as basal synaptic transmission level as control. Synaptic transmission at each time cut was expressed as： p=（ Vdifferentime cut / Vbasal） × 100%. MAIN OUTCOME MEASURES： The differences of synaptic transmission level were compared among the subgroups in the basic group after models also among the subgroups in the HFS group after HFS.RESULTS： All the 60 rats were involved in the analysis of results. ① Comparison of synaptic transmission level at different time cut after modeling and the effect of electroacupuncture in the subgroups of the basic group： The synaptic transmission level in the sham-operated subgroup had no significant change within 120 minutes （P 〉 0.05）. The synaptic transmission levels at 10, 30 and 60 minutes in the model subgroup were obviously lower than those in the sham-operated group [（60±7）%, （90±3）%, （93±4）%; （100±5）%, （102±6）%, （105±7）%, P 〈 0.05-0.01]. With the prolongation of time for ischemia/reperfusion, the synaptic transmission level gradually ascended to the normal level, and those at 90 and 120 minutes were close to those in the sham-operated group （P 〉 0.05）. In the subgroup of electroacupuncture, the synaptic transmission levels at 10, 30, 60, 90 and 120 minutes were obviously higher than those in the model subgroup [（93±5）%, （106±10）%, （123±16）%, （145±20）%, （168±25）%; （96±7）%, （98±8）%, P 〈 0.05-0.01].② Comparison of synaptic transmission level at different time cut after HFS and the effect of electroacupuncture in the groups： In the sham-operated group, the synaptic transmission level after HFS increased significantly, and maintained without decrease within 180 minutes. In the model group, the synaptic transmission level at 0, 10, 30, 60, 120 and 180 minutes after HFS were obviously lower than those in the sham-operated group [（60±7）%, （95±9）%, （138±11）%, （141±13）%, （140±13）%, （138±15）%; （100±6）%, （182±21）%, （179±18）%, （177±18）%, （175±23）%, （178±24）%, P 〈 0.01]. The synaptic transmission level at 60, 120 and 180 minutes after HFS in the electroacupuncture group were close to those in the sham-operated group （P 〉 0.05）, those at 120 and 180 minutes after HFS in the electroacupuncture group were obviously higher than those in the model group [（171±22）%, （181±25）%, P 〈 0.05-0.01]. CONCLUSION： Electroacupuncture could enhance the basic activity of synaptic transmission in the dentate gyros of hippocampus in cerebral ischemic injury in rats. Electroacupuncture has obvious LTP effect on the activity of synaptic transmission induced by HFS.