The Research Of The Relationship Between Neural Cadherin And Mossy Fiber Sprouts In Hippocampus Of Epileptic Rats Induced By Pilocarpine

Objective Epilepsy is a chronic encephalic disease often caused by many reason.It was characterized with neural system dysfunction caused by excessive synchronous discharges, which might lead to neuron function damage and structure rebuilding. Microtubule associated neural cadherin(N-cadherin), a phosphoprotein, could regulate microtubule stability. It was mainly contained in soma and dendrites of neuron, so was regarded as a specific marker for the dendrite. Immunohistochemistry method was applied on hippocampus of pilocarpine induced rats, to determine the N-cadherin immunoreactivity (N-cadherin-IR) with or without diazepam intervention at various time points.Methods 66 healthy male 6-8 weeks old Wistar rats were randomly divided into 3 groups: Group control (A) includes 6 rats. Group experiment (B) and Group diazepam-intervention (C) respectively contain 30 rats. Seizure was induced by Pliocarpine i.p. in Group B and C. The latter group was previously injected diazepam i.p., and A, equal NS. Then the two groups were executed at 1days, 4days, 7days, 14days and 28days after seizure. The brain tissues were studied histologically withHE staining to observe the neuronal alterations microscopically, and immunohistochemistry study was carried out for the observation of the expressions of N-cadherin and Timm's stain of mossy fiber.Results In the Group A, neurons in hippocampus are normal microscopically with homogenous staining by HE. In Group B, however, after treated with pilocarpine, neuronal degeneration is observed in area CA1, CA3, and dentate hilus. The main pathological changes include the loss of neuronal cells, especially the large pyramidal cells and granular cells in dentate gyrus. Acidophilic neurons identified with HE staining appear dark and shrunken, with pyknotic neulei and irregular dispersed chromatin clumps.Immunohistochemistry study showed that, in Group A, N-cadherin--IR was slightly expressed in hippocampal ,where there were a few positive cells ,stained with slight brown.In group B,some positive cells emerged in the cytoplasm and nucleus in area CA₃ and dentate hilus at 4 days,more at 7 days to 14 days,then disappeared gradually.In group C ,the expressed of N-cadherin was mild at 4 days ,slight apparent at 7 days, more at 14 days too,then declined, but significantly weaker than those of group B totally.Timm Stain: In P7, stained granule sedimentations appear in the dentate molecular layer and pyramidal layer of CA3 zone. The granule sedimentations are more stained and become bundle-like or patch-like in P14. And in P28, an obvious stained band is formed. Compared with Group A, Group B induces prominent mossy fiber sprouting. In Group A and Group C, no noticeable granule sedimentations are found.Conclusions Significantly changes of N-cadherin-IR were found in hippocampal CA₃ region after pilocarpine induced seizure, and moreover, the location and time phase of N-cadherin positive dendrites were accorded with mossy fiber sprouting. In additon, diazepam used before seizure alleviated neuron damage which resulted in indistinctive N-cadherin-IR change.