The Research Of Microtubule Associated Protein 2 With The Structure Rebuilding In Hippocampus Of Epileptic Rats Induced By Pilocarpine

Objective Epilepsy is characterized with neural system dysfunction caused by excessive synchronous discharges, which may lead to neuron function damage and structure rebuilding. Microtubule associated protein 2 (MAP2), a phosphoprotein, can regulate microtubule stability. It is mainly contained in soma and dendrites of neurons and is regarded as a specific marker for dendrites. Immunohistochemical method is applied on hippocampus of lithium chloride -pilocarpine induced epileptic rats, to determine the MAP2 immune reactivity (MAP2-IR) and mossy fiber sprouting (MFS) with or without diazepam intervention at various time points.Methods 66 healthy male 6-8 weeks old Wistar rats are randomly divided into 3 groups: Group control (A) includes 6 rats. Group experiment (B) and Group diazepam-intervention (C) respectively contain 30 rats. Seizures are tried to be induced by lithium chloride -pilocarpine i.p. in Group B and C. The rats in Group C are previously injected diazepam 30 minutes before pilocarpine i.p.. Then the rats are respectively executed at 1 days, 4 days, 7 days, 14 days and 28 days after pilocarpine injection. Brain tissues are studied histologically with HE staining to observe the neuronal changes microscopically. Immunohistochemical stain and Timm stain are carried out to observe the expressions of MAP2 and mossy fiber sprouting.Results In 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.Immunohistochemical study: In Group B, the corrected optical density (COD) values of MAP2-IR in the molecular cell layer of hippocampal dentate gyrus obviously increases after 4 days of pilocarpine injection (P4), distinctly boosts after 7 days (P7), reaches summit after 14 days (P14) and comes back to normal level after 28 days of epilptogenesis. MAP2-IR is mainly distributed in dendrites and in neuron bodies in P4, surrounding granular cells with radialized or filar morphology in P7. In P14, the whole molecular layer is fulfilled with MAP2-IR. In Group C, no prominently changes are observed.Timm Stain: In P7, stained granule sedimentations appear in the molecular layer of dentate gyrus and pyramidal layer of CA3 zone. The granule sedimentations are more stained and become bundle-like or patch-like in P14. In P28, an obvious stained band is formed. Compared with Group A, Group B induces prominent mossy fiber sprouting. But in Group A and Group C, no noticeable granule sedimentations are found.Conclusions Significantly changes of MAP2-IR are found in hippocampal dentate gyrus after lithium chloride -pilocarpine induced seizures. Moreover, to a certain extent, the location and time phase of MAP2-IR positive dendrites are accorded with mossy fiber sprouting. In additon, diazepam can effectively cut down seizure attacks.