The Relationship Between The Cognitive Handicap After Seizure And The Changes Of NR2B Expression

Objective: Epilepsy is a common chronic dysencephalia syndromes induced by some diseases. In addition to the seizure, there are cognitive impairment such as scattered attention, learning and memory impairment. Among of these, learning and memory impairment is the most common symptoms for epilepsy patients with cognitive impairment and have caused attentions. However, because the mechanism is not yet clear, so in clinical work people have not find effective ways to prevent and cure it. To discuss the mechanisms and provide effective method to clinical medicine,we observe the effect of pentylenetetrazole(PTZ)-kindled epilepsy on rats'electroencephalogram (EEG),learning and memory and the expression of NMDA receptor type 2 receptor (NR2) B subunit using immunocytochemitry and reverse transcription-polymerase chain reaction (RT-PCR).Methods:1 Model makingUse chronic model of epilepsy induced by PTZ intraperitoneal injection.100 mature male Sprague-Dawley(SD) rats (weight 200±20 g) selected by Y maze were separated into two random groups:chronic epilepsy(CEP) group and normal control(NC) group.CEP rats were injected by PTZ 35 mg/kg every morning and this administration lasted 30 days, while the NC rats were injected by normal sodium. According to Racine criterion, seizure intensity was divided into 6 grades: grade 0: any seizure was not observed; grade I: a little tingling of beards and twitching face; grade II: nodding, chewing accompanying with twitching face or wet dog shakes ; grade III: raising one of a forelimb and clonus; grade IV: standing accompanying with bilateral forelimbs; grade V: standing accompanying with falling down, generalized tonic-clonic seizure. If 3 successive seizures of grade IV or V were observed, the lighting was to be successful.2 Electroencephalogram (EEG)After rats were narcosised by chloral hydrate,using stereotaxic apparatus,we implanted bipolar electrodes in frontal cortexes and hippocampus symmetrically.when the rats waked, we made the models with the methods above-mentioned and recorded the EEG.3 Praxiology detectingThe ability of learning and memory was assessed by the Morris water maze and Y maze on the thirty-first day.4 ImmunocytochemitryAfter praxiology detecting, 8 rats of each group randomly selected were deeply narcosised by chloral hydrate before instillation. After that, the telencephalon was taken out. Then the slides were inlubated with NR2B polyclonal antibody, these specimens were incubated with the secondary antibody, avidin-biotin-perxidase complex. Among these approaches, we should wash these specimens with PBS, the results were visualized by using diaminobenzidine as chromogen.5 Reverse transcription-polymerase chain reaction (RT-PCR)After praxiology detecting,8 rats of each group randomly selected,Then we took the total RNA of hippocampus,and got our products by the process of reversing transcript,lead expanding,electrophoresis of expanding produc tion,fixing quantify and taking a photograth of the electro phoresis bar.Finally,we analyzed the result.Results:1 results of epilepticus modemost of CEP group rats began to stare,nod,wash their face and twitching face from the sixth day to eighth day.Among the eighteenth day and the twenty-forth their muscle began to clonus,their forelimbs began to uplift and tonic clonic seizure at last.About 80% of rats comforted to the Racine criterion.The administration was 30 days.The NC group rats did not appear epileptic seizure.2 EEGIn NC group EEG present a rhythm of 9-11Hz low and middle amplitudeαwave. In CEP group during interphase EEG presented a rhythm of low amplitudeαwave(9-11Hz)with paroxysmal epileptic electric discharges which present high amplitude polispike wave complexes lasting 1-2 seconds. 3 Praxiology detecting3.1 Water maze test 24 hours after seizure, the escape latencies of the CEP group are not significantly different from the NC group(P>0.05),in the second day,it is longer than NC group( P<0.05),and in the third day,the difference is significantly( P<0.01).The times cutting through platform area for searching platform in 120 seconds is less than NC group significantly( P<0.01),the swimming time in the flat quadrant in the CEP group was not significantly different from the NC group(P>0.05)3.2 Y maze test the total error was increase in Y maze test (P<0.05).4 ImmunocytochemistryThe number of NR2B positive cells in CEP hippocampal CA3 decreased significantly(P<0.01).5 RT-PCRThe expression of NR2B mRNA in CEP group was lower than NC group(P<0.01).Conclusion:1 We successfully established CEP animal model using PTZ.2 We can detect cognition ability using water maze and Y maze.3 The dysfunction of cognition responding have a relatinship with the decrease of NR2B expression in hippocampus of rat.