Changes Of P75NTR Expression In Hippocampal Neurons Of Pentylenetetrazole-kindled Rats

Objectives: Epilepsy, which is essentially an abnormality of cerebral function resulting from the discharges of some cerebral neurons in over high excitement state, has been a common clinical syndrome, the mechanics of epilepsy is not known yet.Epilepsy can lead to brain injured. Apoptosis or programmed cell death priming a series of complicate protease enzyme cascade, is an important pathway of brain injured causing by epilepsy. Long period epileptic seizure can show up elective apoptosis, necrosis of neuron and sclerosis of hippocampus. Rats were kinded by PTZ, and induced status epilepticus(SE), changes of behavior were observed, hippocampal neuron loss was detected by histology. Meanwhile, the expression of neurotrophin receptor P75 in the hippocampus was determined by RT-PCR, western blot and immunohistochemistry of SE group and normal control group. To approach the apoptosis correlating pathway mediated by P75NTR, can conduce to search effectively the therapia target through molecular level, thus applying a new way to lessen the brain injured of epilepsy.Methods: Use status epilepticus(SE) model induced by PTZ intraperitoneal injection ,100 mature male Sprague-Dawley(SD) rats (weight 200±20g) were separated into two random groups : status epilepticus group and normal control group. Each group is divided into 1,6,24,72h subset groups. Each group includes 20 rats. Rats were injected by PTZ 40mg/kg, 20mg/kg after 10 mins, 10mg/kg after 10 mins. According to Racine criterion, seizure intensity was divided into 6 grades: grade 0: any seizure was not observe; 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, and SE lasted till 30 mins, the lighting was to be successful. while the NC rats were injected by normal sodium. Changes of behavior were observed. Meanwhile,the expression of neurotrophin receptor P75 in the hippocampus was determined by RT-PCR and western blot of SE group and normal control group. The changes of P75NTR at CA1 and CA3 of hippocampus were observed by immunohistochemistry method.Results:1 results of epilepticus mode: SE group including 80 rats, 16 rats use 40mg/kg, 48 use 60mg/kg,11 use 70 mg/kg,5 use 80mg/kg, began to stare,nod,wash their face and twitching face. Accompanied by injecting every 10 mins, 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. 27 rats died resulting of tonic clonic seizure. The NC group rats did not appear epileptic seizure.2 Changes of histology in hippocampus:In hippocampal area of the rats in NC group, there were intact neurons, distinct structure, uniform chromatin, abundant apparatus. In SE group, however, there were condensed nucleus, edematous neuron, swollen perikaryon with vacuole, softening point foci could be seen in the hippocampus. This change was most obvious in 24h, and in 6h and 72h group, the neuron and neuropile were less swollen, karyotheca were comparatively intact.3 Changes of P75NTR mRNA and protein in hippocampus: The expression of neurotrophin receptor P75 began to increase after 6 hours in SE, and increased the highest in 24 hours(P<0.01),and decreased in 72 hours,but higher than normal control group(P<0.05).There was significantly difference between two different groups(P<0.05).4 Changes of immunological reaction at CA1 and CA3 of hippocampus: the immunoreactant was brown and most of them were in the endochylema of the neuron. The possive cells could be seen obviously after 6 hours in SE, and increased the highest in 24 hours, and decreased in 72 hours. There was significantly difference between different positive cells(P<0.01).Conclusion: 1 PTZ kinding by intraperitoneal injection provides a validated model of postseizure dysfunctioning, which is similar to human being of tonic clonic seizure.2 The expression of neurotrophin receptor P75 began to increase after 6 hours in SE, and increased the highest in 24 hours, and decreased in 72 hours, it shows that seizure can induce neurotrophic factors, especially its receptor and apoptosis relating pathway, which perhaps can contribute to the persistent structure and functional changes of the formation in epilepsy through acting on its receptor.