Background and Purpose-Recently, there has been great interest in adult neurogenesis. We investigated whether transient forebrain ischemia could influence the proliferation of neuronal progenitor in the subgranular zone (SGZ) of the rat hippocampus and whether aging could influence the neurogenesis after ischemia. Methods-Male Wistar rats were subjected to 4-vessel occlusion model. We used a bromodeoxyuridine (BrdU) labeling method to identify the postproliferation cells and double-immunostaining with confocal microscopy to determine the cell phenotype. Results-The number of BrdU-positive cells in the SGZ increased Ϸ5.7-fold 8 days after ischemia, compared with the control. BrdU-positive cells formed clusters, which suggested that these cells had divided from an original progenitor cell, and expressed Musashi1 (Msi1), a marker of neural stem/progenitor cells. Although astrocytes also expressed Msi1 in the adult brain, Msi1-positive cells that formed clusters in the SGZ did not express glial fibrillary acidic protein, an astrocyte marker. About 70% of all BrdU-positive cells in the SGZ represented the neuronal phenotype 4 weeks after the BrdU injection. Although proliferation of progenitor cells was stimulated in both young and older animals, aging accelerated the reduction in newborn cells after ischemia. Conclusions-Our results indicate that ischemic stress stimulated the proliferation of neuronal progenitor cells in the SGZ of both young and old rats but resulted in increased neurogenesis only in young animals. Our findings will be important in developing therapeutic intervention to enhance endogenous neurogenesis after brain injury.

Summary: Cerebral ischemia models using mice have drawn increasing attention, particularly because of the availability of transgenic animals, However, the variability of intracranial vas culature at the circle of Willis in mice can influence the degree of ischemia in both the bilateral common carotid artery (CCA) occlusion and intraluminal suture occlusion models, We have developed a method to predict the extent of the anastomosis between carotid and vertebrobasilar circulation in three mouse strains (C57BLl6, CBA, and DBAl2) by measuring cortical microperfusion with laser Doppler flowmetry during a 1-minute occlusion of both CCA, When animals showed residual cortical microperfusion of less than 12% during bilateral CCA occlusion, the mice showed absence of functional anastomosis, developed ATP depletion in the frontal cortex during occlusion,The patency of the posterior communicating artery (PComA) has been regarded as a crucial factor in the development of forebrain ischemia after bilateral com mon carotid artery (CCA) occlusion in gerbils (Levine and Sohn, 1969;Kahn, 1972; Berry et aI., 1975), In mice, strain differences have been observed regarding the pa tency of the PComA at the circle of Willis (Barone et a!., 1993; Yang et aI., 1997), Although the territory supplied by the posterior cerebral artery (PCA), including the hip pocampus and thalamus, is expected to experience isch- emia using the intraluminal suture occlusion model in the absence of collateral circulation through a patent PComA (Fig. 1), the importance of the PComA has not been critically evaluated in the context of an intraluminal su ture occlusion model to produce occlusion of the middle cerebral artery (MCA), In the current study, we provide evidence that patency of the PComA is a crucial deter minant of the development of bilateral forebrain isch emia after bilateral CCA occlusion as well as ischemia in the PCA territory using the intraluminal suture occlusion model in three murine strains, including C57BL/6, CBA, and DBA12. We therefore developed a procedure to pre dict the patency of the PComA and found that this pro cedure would be useful for the reproducible induction of cerebral ischemia in transgenic mice. MATERIALS AND METHODSThree mouse strains were obtained from Charles River, Inc.(Yokohama, Kanagawa, Japan): C57BLl6NCrj (C57BLl6), CBAljNCrj (CBA), and DBAl2NCrj (DBAl2). All mice were mature males aged 8 to 16 weeks, weighing 22.5 ± 0.4 g (C57BLl6, n = 46), 21.8 ± 0.6 g (CBA, n = 27), and 22.8 ±

Synaptic activity induces changes in the number of dendritic spines. Here, we report a pathway of regulated endocytosis triggered by arcadlin, a protocadherin induced by electroconvulsive and other excitatory stimuli in hippocampal neurons. The homophilic binding of extracellular arcadlin domains activates TAO2beta, a splice variant of the thousand and one amino acid protein kinase 2, cloned here by virtue of its binding to the arcadlin intracellular domain. TAO2beta is a MAPKKK that activates the MEK3 MAPKK, which phosphorylates the p38 MAPK. Activation of p38 feeds-back on TAO2beta, phosphorylating a key serine required for triggering endocytosis of N-cadherin at the synapse. Arcadlin knockout increases the number of dendritic spines, and the phenotype is rescued by siRNA knockdown of N-cadherin. This pathway of regulated endocytosis of N-cadherin via protocadherin/TAO2beta/MEK3/p38 provides a molecular mechanism for transducing neuronal activity into changes in synaptic morphologies.

Background and Purpose-The purpose of this study was (1) to examine the contribution of microglia and macrophages with their interleukin-1␤ production and (2) to assess the vulnerability and response of oligodendrocytes in cerebral infarction. Methods-Male Wistar rats were subjected to permanent occlusion of the left middle cerebral artery. Expansion of ischemic infarction and response of oligodendrocytes were investigated together with accumulation of inflammatory cells, production of interleukin-1␤, and disruption of the blood-brain barrier. Apoptotic cell death was inferred from fragmented DNA and the expression of proapoptotic Bax protein. Results-During expansion of infarction, amoeboid microglia and extravasation of serum albumin were observed not only in the infarcted area but also in the adjacent surviving area, whereas macrophages accumulated along the boundary and granulocytes migrated into the center of the infarction. Both amoeboid microglia and macrophages produced interleukin-1␤, an inflammatory cytokine, during an early ischemic period. Furthermore, macrophages within the infarcted tissue expressed Bax protein and subsequently showed fragmented nuclear DNA. Oligodendrocytes were detected in the infarcted area even after 24 hours following middle cerebral artery occlusion, but they subsequently developed fragmented DNA. A week after onset of ischemia, oligodendrocytes were found to be accumulated in the intact area bordered with the infarct together with reactive astrocytes. Conclusions--Our results suggest the importance of amoeboid microglia, macrophages, and their interleukin-1␤ production in gradual expansion of cerebral infarction. Resident oligodendrocytes may be resistant to ischemic insults, and oligodendrocytes accumulated at the border of the infarction may participate in tissue repair after cerebral infarction.

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