| The study of neurogenesis in the adult brain is among the most exciting and fasting moving areas of neuroscience today. A series of evidence suggests that ongoing neurogenesis in discrete brain regions not only occurs in normal adult mammalian animals, but also is modulated by some physiological factors and pathological events, including learning, running, an enriched environment, seizure, ischemic insult, adrenalectomy, mechanical dentate gyms lesions and so on. These findings provide a new therapeutic strategy for replacing neurons that have been lost to neurodegenerative diseases and cerebral vascular diseases, and also provide a new clue for investigating the plasticity of brain structure andfunction after epileptic seizures. However, the first step we must take at present is to clarify the mechanisms underlying the proliferation of neural precursor cells and the function of new-born neurons in brain, which will be critical elements in unlocking the brain's capacity for self-repair.In this study, we try to explore some issues above mentioned by using pentylenetetrazol(PTZ)-induced seizure model. Firstly, we established an experimental method to visualize neurogenesis in mammalian brain in situ by validating the reliability of BrdU labeling dividing cells and fishing out an appropriate dose of BrdU i.p.. Secondly, we investigated the temporal profile of neural precursor cells proliferation and differention in dentate gyms after PTZ-induced seizures by using BrdU labeling method. Then we discussed the roles of Glu-iGluRs pathway and NOS-NO pathway in enhanced neurogenesis after seizures. Lastly, we determined whether the new neurons in the dentate gyms had the characteristic morphology of functional granule cells, the new neurons can be incorporated into intrinsic neural circuit, and the new neurons can express neurotransmitters. Our results showed:(1) BrdU-immunoreactive cells were confined to the subgranular zone (SGZ) in the dentate gyrus, and displayed oblong or irregularly shaped nuclei when three different doses of doses of BrdU were given to adult mature rats. Cells in 10 mg/kg group were very lightly stained and, in many instances, difficult to see clearly, while cells in 50 mg/kg and 100 mg/kg were very dark and clearly labeled. Double-label immunofluorescence for BrdU and neuron markers showed that majority of BrdU labeled cells in 50 mg/kg group were of a neuronal phenotype and were gradually migrating into the granule cell layer from the SGZ.(2) Quantitative analysis of BrdU labeling revealed a significant increase of the proliferation rate of neural precursor cells in the dentate gyrus 3,7, and 14 d after PTZ-induced seizures compared with controls (P < 0.01). The number of BrdU labeled cells in the dentate gyrus returned to baseline levels by 28 d after the initial seizures. Most of newborn cells migrated into the granule cell layer from the SGZ, displayed the neuronal phenotype.(3) MK-801 (1 mg/kg i.p.) significantly reduced the number of BrdU labeled cells in the dentate gyrus 3, 7, and 14 d after PTZ-induced seizures (P < 0.01), and inhibited the proliferation rate of neural precursor cells in the dentate gyrus. DNQX injected (15 mg/kg i.p.) 30 nun before PTZ significantly reduced the number of BrdU labeled cells in the dentate gyrus at the 3rd d after seizures (P < 0.01), but did not influence the number at the 7th d and the 14th d after seizures.(4) L-Arg (200 mg/kg i.p.) did not change the proliferation rate of neural stem cells or progenitor cells in the dentate gyrus 3 d and 14 d after PTZ-induced seizures, but significantly increased the number of BrdU labeled cells in the dentate gyrus at the 7th d after seizures (P < 0.01). 7-NI injected (50 mg/kg i.p.) 10 min before PTZ significantly reduced the number of BrdU labeled cells in the dentate gyms at various time points after seizures (P < 0.01) with a prominent inhibition on the cell proliferation at the 3rd d. Aminoguanidine administered with 100 mg/kg i.p. also significantly inhibited the proliferati...
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